WBBSE Solutions For Class 10 Physical Science And Environment Physical And Chemical Properties Of Elements Inorganic Chemistry In Laboratory And Chemical Industry

Inorganic Chemistry In Laboratory And Chemical Industry Topic A Ammonia And Urea Synopsis

WBBSE Class 10 Physical and Chemical Properties Overview

Laboratory preparation of NH3: Ammonia (NH3) is prepared in the laboratory by heating a mixture of ammonium chloride and anhydrous slaked lime taken in a ratio of 1 : 3 by mass.

Drying and collection of NH3: Water vapour is then removed from the ammonia gas by passing the gas through a column of quick lime and then it is collected by downward displacement of air.

Physical properties of NH3: Ammonia is a colourless and pungent-smelling gas. It is highly soluble in water. A saturated aqueous solution of ammonia having a specific gravity of 0.88 is known as liquor ammonia.

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Chemical properties of NH3:
1. The aqueous solution of ammonia is alkaline in nature.
2. Ammonia exhibits strong reducing property and can precipitate metal ions such as Fe3+, Al3+ etc., as insoluble hydroxides from their aqueous solution.
3. Nessler’s reagent turns brown in presence of ammonia.
4. When excess NH3 gas is passed through  CuSO4 solution, the solution turns deep blue.

Wbbse Class 10 Inorganic Chemistry

Industrial preparation of ammonia by Haber’s process: Ammonia is industrially prepared by Haber’s process by the direct combination of 1 volume of N2 gas and 3 volumes of H2 gas. The reaction is carried out at an optimum temperature and a pressure of 450°C and 200 atm respectively. Iron oxide is used as the catalyst and a mixture of K2O and Al2O3 is used as the promoter in this reaction.

Preparation of urea: Urea [CO(NH2)2] is commercially manufactured by heating a mixture of liquid NH3 and CO2 gas in a closed vessel at 170-190°C temperature and a pressure of about 175 atm.

Reactions:

⇒ \(\begin{aligned}
2 \mathrm{NH}_3+\mathrm{CO}_2 & \rightleftharpoons \mathrm{H}_2 \mathrm{NCOONH}_4 \\
\mathrm{H}_2 \mathrm{NCOONH}_4 & \rightleftharpoons \mathrm{H}_2 \mathrm{NCONH}_2+\mathrm{H}_2 \mathrm{O}
\end{aligned}\)

Uses of ammonia:

1. NH3 gas and aqueous solution of ammonia are extensively used in the laboratories as important reagents.
2. Liquid ammonia is used as a refrigerant in refrigerators, cold storages and ice manufacturing units.
3. Ammonia is also used to prepare urea.

Uses of urea:
1. Urea is widely used as nitrogenous fertiliser.
2. It is also used in the preparation of different medicines such as urea stibamine, barbiturates etc.
3. It is also used in the commercial preparation of nitrocellulose, cellophane etc.

WBBSE Solutions For Class 10 Physical Science And Environment Physical And Chemical Properties Of Elements Inorganic Chemistry In Laboratory And Chemical Industry

Inorganic Chemistry In Laboratory And Chemical Industry Topic A Ammonia And Urea Short And Long Answer Type Questions

 

Question 1. Why is concentrated H2SO4 or phosphorus pentoxide ( P2O5) or anhydrous CaCI2 not used to dry NH3 gas prepared in the laboratory?

Answer: Ammonia being a basic compound cannot be dried by using concentrated H2SO4 or P2O5 as these are acidic in nature. This is because concentrated H2SO4 and P2O5 react with ammonia to produce ammonium sulphate and ammonium phosphate respectively.

\(\begin{gathered}
2 \mathrm{NH}_3+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow\left(\mathrm{NH}_4\right)_2 \mathrm{SO}_4 \\
6 \mathrm{NH}_3+\mathrm{P}_2 \mathrm{O}_5+3 \mathrm{H}_2 \mathrm{O} \rightarrow 2\left(\mathrm{NH}_4\right)_3 \mathrm{PO}_4
\end{gathered}\)

 

On the other hand, anhydrous CaCI2 absorbs ammonia to form an addition compound. Hence, it is also not suitable to dry NH3 gas prepared in the laboratory.

\(\mathrm{CaCl}_2+8 \mathrm{NH}_3 \rightarrow \mathrm{CaCl}_2 \cdot 8 \mathrm{NH}_3\)
additional compound

Wbbse Class 10 Physical Science Solutions

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Question 2. What precautionary measures should be taken if an accident occurs due to leakage of ammonia gas in cold storages, factories or from storage tanks containing ammonia?

Answer: Ammonia is a basic gas with a characteristic strong, pungent smell. It is extremely harmful to eyes and can cause respiratory troubles if it is inhaled.

Large quantities of ammonia can dissolve in a small volume of water. So, in case of ammonia leakage, the eyes and face of the affected person should be immediately washed with plenty of water and the face of the person should be covered with a wet cloth or handkerchief to avoid further contact with ammonia.

Then the person should be immediately taken to the doctor. In addition to this, plenty of water should be sprayed at the site of the leakage so that ammonia gas present in the air is absorbed by water, thereby diminishing the chance of further harmful effects.

Question 3. State the principle and suitable chemical equation for the industrial preparation of Urea.

Answer:

The principle and suitable chemical equation for the industrial preparation of Urea

Urea is industrially prepared by heating a mixture of liquid ammonia and carbon dioxide gas in a closed vessel at around 170-190°C and under 175 atmospheric pressure.

Chemical equation: The reaction takes place in two steps—
1. In the first step, liquid ammonia and carbon dioxide gas react with each other to form ammonium carbamate (H2NCOONH4). This step is reversible in nature.

\(2 \mathrm{NH}_3+\mathrm{CO}_2 \rightleftharpoons \mathrm{H}_2 \mathrm{NCOONH}_4\)

2. In the second step, ammonium carbamate decomposes to form urea (H2NCONH2). This step is also reversible in nature.

\(\mathrm{H}_2 \mathrm{NCOONH}_4 \rightleftharpoons \mathrm{H}_2 \mathrm{NCONH}_2+\mathrm{H}_2 \mathrm{O}\)

Wbbse Class 10 Physical Science Solutions

The first step almost proceeds towards completion, but in the second step only 40-60% of ammonium carbamate gets converted into urea.

Question 4. Mention some important uses of ammonia in different industries.

Answer:

Important uses of ammonia are—

1. Ammonia is used to manufacture important nitrogenous fertilisers such as ammonium sulphate, ammonium nitrate, ammonium phosphate, urea etc.
2. It is used to produce nitric acid by Ostwald’s process and sodium carbonate by Solvay process.
3. Liquid ammonia is used as a refrigerant in cold storages, ice factories, refrigerators etc.

Question 5. State some important uses of urea.

Answer:

Some important uses of urea are—

1. It is extensively used as a nitrogenous fertiliser for agricultural purposes.
2. Urea stibine, a medicine for treating of Kala-azar, is prepared from urea. Barbiturates (a kind of sedative) is also made from urea.
3. Urea is used as a raw material in the industrial preparation of cellophane papers, rayons, nitrocellulose (an explosive) etc. It is used to make urea-formaldehyde resin.

Understanding Inorganic Chemistry in Industry

Question 6. State the principle and chemical reactions involved in the laboratory preparation of ammonia.

Answer:

The principle and chemical reactions involved in the laboratory preparation of ammonia

Principle: In the laboratory, ammonia is prepared by heating a mixture of ammonium chloride (NH4CI) and slaked lime [Ca(OH)2] or quick lime (CaO).

Chemical reactions:

\(\begin{gathered}
2 \mathrm{NH}_4 \mathrm{Cl}+\mathrm{Ca}(\mathrm{OH})_2 \rightarrow 2 \mathrm{NH}_3 \uparrow+\mathrm{CaCl}_2+2 \mathrm{H}_2 \mathrm{O} \\
2 \mathrm{NH}_4 \mathrm{Cl}+\mathrm{CaO} \rightarrow 2 \mathrm{NH}_3 \uparrow+\mathrm{CaCl}_2+\mathrm{H}_2 \mathrm{O}
\end{gathered}\)

WBBSE Solutions For Class 10 Physical Science And Environment Physical And Chemical Properties Of Elements Inorganic Chemistry In Laboratory And Chemical Industry Laboratory Preparation Of Ammonia

 

Question 7. How is water vapour removed from ammonia gas produced in the laboratory? Why is a particular drying agent used in this case?

Answer:

Water vapour removed from ammonia gas produced in the laboratory As follows:

1. Ammonia gas produced in the laboratory is passed through a column containing quick lime (CaO) with the help of a delivery tube. Quick lime absorbs water vapour present in ammonia gas and as a result, dry ammonia gas is obtained.

2. NH3, being a basic compound, cannot be dried up using acidic compounds. Hence a particular drying agent should be used to dry ammonia. Therefore a basic substance, such as quick lime (CaO) is used for drying ammonia in the laboratory.

Question 8. In the laboratory preparation of ammonia, NH4CI and Ca(OH)2 are mixed thoroughly in their dry states and then heated. Why?

Answer:

In the laboratory preparation of ammonia, NH4CI and Ca(OH)2 are mixed thoroughly in their dry states and then heated

Dry NH4CI undergoes sublimation on heating, /.e., it directly vapourises from its solid state. So, if NH4CI and Ca(OH)2 are not mixed thoroughly, NH4CI on heating will sublime and get eliminated from the reaction mixture.

The mixture of NH4CI and Ca(OH)2 is heated in their dry states because ammonia is highly soluble in water and thus, on heating its aqueous solution, ammonia gas cannot be obtained in its free state.

Wbbse Class 10 Physical Science Solutions

Question 9. How will you prepare ammonia gas in the laboratory at room temperature?

Answer: When liquor ammonia is added dropwise on solid caustic potash or caustic soda, water gets absorbed by the alkali thereby liberating ammonia gas.

Question 10. Why is liquid ammonia used as a refrigerant?

Answer: The latent heat of vaporisation of liquid ammonia is very high. So, it absorbs large amounts of heat from the surroundings during evaporation. This physical property of liquid ammonia makes it very useful as a refrigerant.

Question 11. We get a strong pungent smell of ammonia near laboratories and stables. Why?

Answer:

We get a strong pungent smell of ammonia near laboratories and stables.

The urine of humans and other mammals contains urea (NH2CONH2) which is decomposed by bacteria to produce ammonia. This is why we get a strong pungent smell of ammonia near laboratories and stables.

Question 12. Is it justified to term the aqueous solution of ammonia as ammonium hydroxide?

Answer: There is no existence of NH4OH molecules in the aqueous solution of ammonia. So, an aqueous solution of ammonia cannot be termed as ammonium hydroxide rather, it is justified to term it as aqueous ammonia.

Question 13. Write with equation what happens hydrogen chloride gas.

Answer: When ammonia gas comes in contact with hydrogen chloride gas, dense white fumes are formed. These fumes are actually the aggregation of fine ammonium chloride (NH4CI) particles floating in air.

\(\mathrm{NH}_3(g)+\mathrm{HCl}(g) \rightarrow \mathrm{NH}_4 \mathrm{Cl}(s)\)


Question 14. Write with equation what happens when chlorine gas reacts with excess ammonia.

Answer: When chlorine gas reacts with excess ammonia, the latter gets oxidised to nitrogen while the former gets reduced to ammonium chloride.

\(8 \mathrm{NH}_3+3 \mathrm{Cl}_2 \rightarrow \mathrm{N}_2 \uparrow+6 \mathrm{NH}_4 \mathrm{Cl}\)


Question 15. Give an example of the reducing property of ammonia.

Answer:

An example of the reducing property of ammonia

When ammonia is passed over heated cupric oxide, the latter is reduced to form red metallic copper and ammonia itself gets oxidised to nitrogen.

\(3 \mathrm{CuO}(s)+2 \mathrm{NH}_3(g) \stackrel{\Delta}{\longrightarrow} 3 \mathrm{Cu}(s)+\mathrm{N}_2(g)+3 \mathrm{H}_2 \mathrm{O}(g)\)

Common Inorganic Compounds and Their Uses


Question 16. Write with equation what happens when ammonia gas is passed over heated lead oxide.

Answer: When ammonia is passed over heated lead oxide, yellow-coloured lead oxide is reduced to form a grey precipitate of metallic lead while ammonia itself gets oxidised to nitrogen.

\(\underset{\substack{\text { (yellow) }}}{3 \mathrm{PbO}}+2 \mathrm{NH}_3 \rightarrow \underset{\text { (grey) }}{3 \mathrm{~Pb}}+\mathrm{N}_2+3 \mathrm{H}_2 \mathrm{O}\)


Question 17. Write with equation what happens when an aqueous solution of ammonia is added to an aqueous solution of ferric chloride.

Answer: When an aqueous solution of ammonia is added to a yellow-coloured solution of ferric chloride, a brown precipitate of ferric hydroxide is produced.

\(\begin{aligned}
& \mathrm{FeCl}_3+3 \mathrm{NH}_3+3 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Fe}(\mathrm{OH})_3 \downarrow+3 \mathrm{NH}_4 \mathrm{Cl} \\
& \text { (yellow } \\
& \text { solution) } \\
&
\end{aligned}\)
Question 18. What happens when aqueous solution of ammonia is added to an aqueous solution of aluminium chloride? Give equation.

Answer: When aqueous solution of ammonia is added to a colourless aqueous solution of aluminium chloride, a white gelatinous precipitate of aluminium hydroxide is produced.

\(\begin{aligned}
& \mathrm{AlCl}_3+3 \mathrm{NH}_3+3 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Al}(\mathrm{OH})_3 \downarrow+3 \mathrm{NH}_4 \mathrm{Cl} \\
& \text { (colourless } \\
& \text { solution) } \\
&
\end{aligned}\)

Question 19. What happens when ammonia reacts With excess chlorine gas? Give equation.

Answer: When ammonia reacts with excess chlorine gas, a yellow-coloured oily explosive compound, nitrogen trichloride (NCl3) is formed along with hydrogen chloride.

Reaction: \(\mathrm{NH}_3+3 \mathrm{Cl}_2 \rightarrow \mathrm{NCl}_3+3 \mathrm{HCl}\)

Question 20. What happens when ammonia is oxidised in presence of a catalyst? Give equation.

Answer: When a mixture of ammonia and excess oxygen is passed over heated platinum or a wire-gauze made of platinum-rhodium alloy (catalyst) at around 700°C, ammonia is oxidised to produce nitric oxide.

Reaction: \(4 \mathrm{NH}_3+5 \mathrm{O}_2 \rightarrow 4 \mathrm{NO}+6 \mathrm{H}_2 \mathrm{O}\)

Question 21. What is meant by liquor ammonia’ and ‘liquid ammonia’?

Answer:
Liquor ammonia: A concentrated aqueous solution of ammonia containing 35% ammonia is known as ‘liquor ammonia’. It has a specific gravity of almost 0.88.

Liquid ammonia: Ammonia is condensed to a colourless liquid at around -33.4°C temperature and at normal atmospheric pressure. This is known as ‘liquid ammonia’.

Question 22. Why. is a bottle containing liquor ammonia cooled before opening?

Answer: In a bottle of liquor ammonia, ammonia gas is dissolved in water under high pressure. So, when the bottle is opened, the ammonia gas dissolved in water immediately comes out of the bottle with great force.

This may cause serious eye injuries. On the other hand, if the bottle is cooled, then the solubility of ammonia in water increases as a result of which the pressure inside the bottle decreases. So on opening the bottle, ammonia does not spout.

Question 23. What changes are observed when an aqueous solution of ammonia is added to an aqueous solution of copper sulphate?

Answer: When an aqueous solution of ammonia is added to a blue coloured aqueous solution of copper sulphate, initially a bluish-white precipitate is formed. On addition of the excess ammonia solution, the precipitate dissolves and the solution turns deep blue.

Question 24. What is Nessler’s reagent? What happens when ammonia comes in contact with Nessler’s reagent?

Answer:

Nessler’s reagent:

1. An alkaline solution of potassium mercuric iodide [K2Hgl4] is known as Nessler’s reagent.
2. When ammonia comes in contact with a small amount of Nessler’s reagent it forms a brown solution. When excess ammonia is passed through Nessler’s reagent, a brown precipitate is formed.

Question 25. State the principle of preparation of ammonia by Haber’s process along with suitable chemical equation.

Answer:

The principle of preparation of ammonia by Haber’s process along with suitable chemical equation

When a mixture of nitrogen and hydrogen (in the volumetric ratio of 1:3) is heated at a temperature of about 450°C and 200 atmospheric pressure in the presence of iron oxide as catalyst and a mixture of  K2O and Al2O3 as promoter, ammonia gas is produced by the direct combination of nitrogen and hydrogen.

Chemical equation: \(\mathrm{N}_2(g)+3 \mathrm{H}_2(g) \rightleftharpoons 2 \mathrm{NH}_3(g)+22.4 \mathrm{kcal}\)

Question 26. Why is Ca(OH)2 more acceptable than NaOH in the laboratory preparation of ammonia?

Answer:

Ca(OH)2 is more acceptable than NaOH due to the following reasons:

1. Ca(OH)2 is cheaper and easily available.
2. Ca(OH)2 does not absorb moisture from air like NaOH.

Question 27. How is the dry ammonia gas collected at laboratory? Why is ammonia gas not collected by the downward displacement of water?

Answer:
1. Ammonia gas is lighter than air. Hence, at the laboratory, the dry ammonia gas is collected by the downward displacement of air in an inverted dry gas jar.
2. Ammonia gas is highly soluble in water. Hence, if it is collected by downward displacement of water it promptly gets dissolved in the water and forms ammonium hydroxide. Moreover to fill the vacuum caused by the dissolution of ammonia, water enters the hot round bottom flask. As a consequence the flask bursts. That is why ammonia is not collected by downward displacement of water.

Question 28. Why aqueous solution of ammonia can not be concentrated by heating?

Answer: On applying heat to the aqueous solution of ammonia, the dissolved ammonia gets evaporated from the solution. Hence amount of ammonia in the solution gets reduced and the solution becomes diluted instead of getting concentrated.

Question 29. Show with example that ammonia gas is basic in nature.

Answer:

Ammonia gas is basic in nature:

1. Ammonia gas turns moist red litmus paper blue.
2. Ammonia reacts with different acids like HCI, H2SO4,  HNO3 etc. to produce ammonium chloride (NH4CI), ammonium sulphate [(NH4)2SO4], ammonium nitrate (NH4NO3) etc. respectively.

\(\begin{gathered}
\mathrm{NH}_3+\mathrm{HCl} \rightarrow \mathrm{NH}_4 \mathrm{Cl} \\
\mathrm{NH}_3+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow\left(\mathrm{NH}_4\right)_2 \mathrm{SO}_4 \\
\mathrm{NH}_3+\mathrm{HNO}_3 \rightarrow \mathrm{NH}_4 \mathrm{NO}_3
\end{gathered}\)

The above facts proves that ammonia gas is basic in nature.

Question 30. What is vanishing ink? Why is it named so?

Answer:

Vanishing ink:

1. The aqueous solution of ammonia mixed with a few drops of phenolphthalein indicator is called vanishing ink. The solution is pink in colour.
2. The aqueous solution of ammonia is alkaline in nature. On addition of a few drops of phenolphthalein the solution turns pink. Since ammonia is volatile in nature it evaporates from the solution. As a result the solution becomes neutral is nature. As phenolphthalein is colourless in neutral medium, the pink colour of the ammonia solution vanishes after some time. Hence it is called Vanishing ink’.

Laboratory Techniques in Inorganic Chemistry

Question 31. What happens when ammonia gas is passed over heated sodium metal? How the ammonia gas be regenerated from the product?

Answer: When ammonia gas is passed over heated sodium at 360°C white wax like solid sodamide or sodium amide and hydrogen gas are formed.

\(2 \mathrm{Na}+2 \mathrm{NH}_2 \rightarrow 2 \mathrm{NaNH}_2+\mathrm{H}_2\)
(Sodamide)

When water is added to sodamide, pungent smelling ammonia gas is regenerated.

\(\mathrm{NaNH}_2+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{NaOH}+\mathrm{NH}_3\)

Question 32. Of the two aqueous solutions one ischloride. How do you identify the ferric chloride solution by using aqueous solution of ammonia? Answer with balanced equations.

Answer: Addition of aqueous solution of ammonia to each of the results of the given solution in the formation of white gelatinous precipitate in one case and formation of brown precipitate in the other. White gelatinous precipitate is for aluminium hydroxide (AI(OH)3) and the brown precipitate is for ferric hydroxide ([Fe(OH)3]).

Hence the solution that contains ferric chloride becomes brown after addition of aqueous solution of ammonia due to the formation of ferric hydroxide.

\(\mathrm{AlCl}_3+3 \mathrm{NH}_4 \mathrm{OH} \rightarrow \mathrm{Al}(\mathrm{OH})_3+3 \mathrm{NH}_4 \mathrm{Cl}\)
Aluminium             Ammonium                         Aluminium
chloride                   hydroxide                          hydroxide

\(\mathrm{FeCl}_3+3 \mathrm{NH}_4 \mathrm{OH} \rightarrow \mathrm{Fe}(\mathrm{OH})_3+3 \mathrm{NH}_4 \mathrm{Cl}\)
Ferric         Ammonium          Ferric
chloride     hydroxide             hydroxide

Question 33. Prove that ammonia contains hydrogen.

Answer:

Ammonia contains hydrogen:

When ammonia gas is passed over heated (360°C) sodium metal, a colourless odourless gas is formed. If a lighted splint is exposed to the gas, it starts burning with a squeaky pop and a blue flame but the flaming splint gets extinguished. Hence the gas is hydrogen and this hydrogen comes from ammonia. Hence it can be concluded that ammonia contains hydrogen.

\(2 \mathrm{Na}+2 \mathrm{NH}_3 \rightarrow 2 \mathrm{NaNH}_2+\mathrm{H}_2\)

 

Question 34. Prove that ammonia contains nitrogen.

Answer:

Ammonia contains nitrogen:

When ammonia gas is passed over heated cupric oxide, a colourless and odourless gas is obtained. Now if a burning Mg-ribbon is introduced to the gas, it continues burning and a white residue is produced.

The white residue, such obtained, when boiled with water, a pungent smelling gas evolves which turns the alkaline Nessler’s reagent brown. Therefore, this pungent smelling gas is ammonia. Hence the white residue is of magnesium nitride and the colourless, odourless gas is nitrogen. So it can be concluded that ammonia contains nitrogen.

\(\begin{gathered}
3 \mathrm{CuO}+2 \mathrm{NH}_3 \rightarrow 3 \mathrm{Cu}+\mathrm{N}_2+3 \mathrm{H}_2 \mathrm{O} \\
3 \mathrm{Mg}+\mathrm{N}_2 \rightarrow \mathrm{Mg}_3 \mathrm{~N}_2 \\
\mathrm{Mg}_3 \mathrm{~N}_2+6 \mathrm{H}_2 \mathrm{O} \rightarrow 3 \mathrm{Mg}(\mathrm{OH})_2+2 \mathrm{NH}_3
\end{gathered}\)


Question 35. A chloride salt ‘A’ is heated with lime to produce a gas reacts with HCI vapour to regenerate ‘A’. Identify ‘A’ and ‘8’. Write down the corresponding equations.

Answer:

A chloride salt ‘A’ is heated with lime to produce a gas reacts with HCI vapour to regenerate ‘A’. Identify ‘A’ and ‘8’.

1. A is NH4CI (ammonium chloride)
B is NH3 (ammonia)

2. \(2 \mathrm{NH}_4 \mathrm{Cl}+\mathrm{CaO} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{NH}_3+\mathrm{CaCl}_2+\mathrm{H}_2 \mathrm{O}\)

\(\mathrm{NH}_3+\mathrm{HCl} \rightarrow \mathrm{NH}_4 \mathrm{Cl}\)


Question 36. Two colourless gases react to form a pungent smelling gas which forms a dense white fume when a glass rod dipped in dilute HCI is held in it. Identify the three gases.

Answer:

Two colourless gases react to form a pungent smelling gas which forms a dense white fume when a glass rod dipped in dilute HCI is held in it.

The pungent smelling gas forms dense white fumes when the glass rod dipped in dilute HCI is held in it. Therefore the pungent smelling gas is ammonia (NH3).

Now ammonia is produced by the reaction of N2 and H2 which are colourless gases. Hence the gases are N2, H2 and NH3.

\(\mathrm{N}_2+3 \mathrm{H}_2 \rightarrow 2 \mathrm{NH}_3 ; \mathrm{NH}_3+\mathrm{HCl} \rightarrow \mathrm{NH}_4 \mathrm{Cl}\)

 

Question 37. Differentiate between liquor ammonia and liquid ammonia.

Answer:

Difference between liquor ammonia and liquid ammonia:

Liquor Ammonia Liquid Ammonia
1. Concentrated aqueous solution of ammonia (specific gravity 0.88), where 35% ammonia is dissolved in water under high pressure, is termed as liquor ammonia. 1. Under normal atmospheric pressure, ammonia gas when cooled down at -33.4°C, it transforms into a colourless liquid. This liquid is known as liquid ammonia.
2. It is used as an important reagent in qualitative analysis to identify several cations. 2.  It is used as a refrigerant in cold storage and in ice factories.
3. Liquor ammonia is a solution where ammonia is solute and water is the solvent. 3. Liquid ammonia is a pure substance.

 

Inorganic Chemistry In Laboratory And Chemical Industry Topic A Ammonia And Urea Very Short Answer Type Questions Choose The Correct Answer

Question 1. Which of the following substances is present in the urine of animals?

  1. NH4CI
  2. (NH4)2SO4   
  3. CO(NH2)2
  4. Ca(OH)2    

Answer: 3. CO(NH2)2

Question 2. Which of the following does not react with water to form ammonia?

  1. Mg3N2
  2. NO2
  3. AIN
  4. CaNCN

Answer: 2. NO2

Question 3. Ammonia is dried by using

  1. P2O
  2. Anhydrous CaCl
  3. Concentrated H2SO4
  4. Quick lime (CaO)

Answer: 4. Quick lime (CaO)

Question 4. The nature of aqueous solution of ammonia

  1. Is acidic
  2. Is alkaline
  3. Is neutral
  4. Changes according to conditions

Answer: 2. Is alkaline

Question 5. If excess ammonium hydroxide is added to copper sulphate solution, then the solution turns

  1. Deep red
  2. Deep yellow
  3. Deep violet
  4. Deep blue

Answer: 4. Deep blue

Question 6. In the presence of Nessler’s reagent, ammonia turns

  1. Black
  2. Green
  3. Brown
  4. Yellow

Answer: 3. Brown

Question 7. The catalyst used in the catalytic oxidation of ammonia to produce NO is

  1. MnO2
  2. Platinum
  3. Iron
  4. Copper

Answer: 2. Platinum

Question 8. The amount of ammonia present in liquor ammonia is

  1. 25%
  2. 30%
  3. 35%
  4. 45%

Answer: 3. 35%

Question 9. The industrial preparation of ammonia is carried out by

  1. Ostwald’s process
  2. Solvay process
  3. Bayer’s process
  4. Haber’s process

Answer: 4. Haber’s process

Question 10. The catalyst used in the preparation of ammonia by Haber’s process is

  1. MnO2
  2. Platinum
  3. Iron oxide
  4. Copper

Answer: 3. Iron oxide

Question 11. The reaction involved in the production of ammonia by Haber’s process is a type of

  1. Isochoric reaction
  2. Isobaric reaction
  3. Endothermic reaction
  4. Exothermic reaction

Answer: 4. Exothermic reaction

Question 12. Which of the following is used as a promoter in Haber’s process of ammonia synthesis?

  1. K2O, Al2O
  2. Na2O, AI2(SO4)3
  3. Na2O, Al2O
  4. K2O, AI2(SO4)3

Answer: 1. K2O, Al2O

Question 13. The volumetric ratio in which N2 and H2 are mixed in Haber’s process is

  1. 2:3
  2. 3:1
  3. 1:3
  4. 3:2

Answer: 3. 1:3

Question 14. The compound formed in the first step of the industrial preparation of urea is

  1. Ammonium carbamate
  2. Ammonium carbonate
  3. Ammonium sulphate
  4. Ammonium sulfite

Answer: 1. Ammonium carbamate

Question 15. The aqueous solution of which of the following salts does not form any precipitate when NH3 gas or NH40H solution is passed through it?

  1. CuSO4
  2. AlCl3
  3. FeCl3
  4. NH4NO3

Answer: 4. NH4NO3

Question 16. Ammonia does not react with

  1. NaOH
  2. H2SO
  3. HCl
  4. H3PO4

Answer: 1. NaOH

Question 17. Ammonia gas is collected at laboratory by

  1. Upward displacement of air
  2. Upward displacement of water
  3. Downward displacement of air
  4. Downward displacement of water

Answer: 3. Downward displacement of air

Question 18. The optimum temperature for the industrial preparation of ammonia in Haber’s process

  1. 723°C
  2. 723K
  3. 813K
  4. 823K

Answer: 2. 723K

Question 19. On cooling ammonia gas converts to a colourless liquid at

  1. 0°C
  2. 25°C
  3. -33.4°C
  4. 30°C

Answer: 3. -33.4°C

Question 20. Which of the following metallic salt solutions reacts with aqueous solution of NH3 to form a brown precipitate?

  1. Al3+ salt
  2. Cu2+ salt
  3. Fe3+ salt
  4. Ni2+ salt

Answer: 3. Fe3+ salt

Question 21. Which of the following gases can be identified by Nessler’s reagent?

  1. NH3
  2. H2S
  3. N2
  4. CO2  

Answer: 1. NH3

Question 22. Which of the following is obtained by heating ammonium carbamate?

  1. NH3
  2. CO(NH2)2
  3. CO2  
  4. N2

Answer: 2. CO(NH2)2

Question 23. Which of the following is obtained by heating ammonium nitrate and calcium oxide?

  1. N2  
  2. NO2
  3. NH3
  4. NO

Answer: 3. NH3

Question 24. Which of the following forms a brown precipitate with ferric chloride solution?

  1. NH4Cl
  2. NH4OH
  3. NaCl
  4. CuSO4

Answer: 2. NH4OH

Question 25. Substance used in the preparation of medicine of human leishmaniasis is

  1. Ammonia
  2. Hydrogen sulphide
  3. Urea
  4. Sulphuric acid

Answer: 3. Urea

Question 26. Solubility of which gas in water is the highest?

  1. N2  
  2. NH3
  3. H2S
  4. CO2  

Answer: 2. NH3

Question 27. Which of the following is used in ice factories for cooling purpose?

  1. NH3
  2. CO2  
  3. NH4OH
  4. CHCl3

Answer: 1. NH3

Question 28. The gas formed by passing NH3 gas over heated CuO is

  1. H2
  2. O2
  3. H2S
  4. N2  

Answer: 4. N2

Question 29. Which of the following creates white fumes with HCI?

  1. CO2
  2. H2S
  3. N2  
  4. NH3

Answer: 4. NH3

Question 30. Formula of Nessler’s reagent is

  1. K2Hgl4 + KOH
  2. K2SO4.10H2O + KOH
  3. K2HgCl4 + KOH
  4. K2Mgl4 + KOH

Answer: 1. K2Hgl4 + KOH

Inorganic Chemistry In Laboratory And Chemical Industry Topic A Ammonia And Urea Answer In Brief


Question 1. Name the chemical substances required for the laboratory preparation of ammonia.

Answer: Ammonium chloride (NH4Cl) and dry slaked lime [Ca(OH)2] are used for the laboratory preparation of ammonia.

Question 2. What happens when moist ammonia gas is treated with phosphorus pentoxide?
Answer: Moist ammonia gas reacts with phosphorus pentoxide (P2O5) to form ammonium phosphate [(NH4)3PO4] salt.

Question 3. What is the specific gravity of liquor ammonia?
Answer: Specific gravity of liquor ammonia is 0.88.

Question 4. Write down the formula of the addition compound formed when ammonia is absorbed by anhydrous CaCI2.
Answer: The formula of the addition compound is CaCI.8NH3.

Question 5. Write the name of the oily explosive liquid that is produced by the reaction of excess chlorine with ammonia.
Answer: The oily explosive liquid .is nitrogen trichloride (NCI3).

Question 6. What can be concluded from the fountain experiment?
Answer: The fountain experiment proves that ammonia is highly soluble in water and its aqueous solution is alkaline in nature.

Question 7. Give an example of a reaction where two gases react to form a solid.
Answer: When ammonia gas reacts with hydrogen chloride gas, dense white fumes of solid ammonium chloride (NH4CI) are formed.

\(\mathrm{NH}_2(g)+\mathrm{HCl}(g) \rightarrow \mathrm{NH}_4 \mathrm{Cl}(s)\)

Chemical Properties of Metals vs. Nonmetals


Question 8. Which gas is produced by the combustion of ammonia gas in the presence of oxygen?

Answer: Nitrogen (N2) gas is produced.

Question 9. What is the colour of the precipitate formed when ammonia gas is passed through aqueous solution of ferric salts?
Answer: Reddish brown precipitate of ferric hydroxide [Fe(OH)3] is formed in this case.

\(\mathrm{FeCl}_3+3 \mathrm{NH}_4 \mathrm{OH} \rightarrow \mathrm{Fe}(\mathrm{OH})_3 \downarrow+3 \mathrm{NH}_4 \mathrm{Cl}\)

 

Question 10. What is the colour of the precipitate formed when ammonia gas is passed through aqueous solution of aluminium salts?
Answer: In this case, white gelatinous precipitate of aluminium hydroxide [Al(OH)3] is formed.

\(\mathrm{AlCl}_3+3 \mathrm{NH}_4 \mathrm{OH} \rightarrow \mathrm{Al}(\mathrm{OH})_3 \downarrow+3 \mathrm{NH}_4 \mathrm{Cl}\)


Question 11. Why should a bottle of liquor ammonia always be cooled before opening?

Answer: On cooling, the solubility of ammonia in water increases which prevents accidental spouting of NH3 gas from the bottle.

Question 12. Name an inorganic fertilizer which is prepared from ammonia.
Answer: An inorganic fertiliser which is prepared from ammonia is ammonium phosphate [(NH4)PO4].

Question 13. Name the chemical compounds that are used as raw materials for the industrial preparation of urea.
Answer: Liquid ammonia and carbon dioxide are used as raw materials for the industrial preparation of urea.

Question 14. What is the percentage of nitrogen present in urea?
Answer: The amount of nitrogen present in urea is almost 46% by mass.

Question 15. Which nitrogenous organic compound is used to prepare medicine for kala azar or black fever?
Answer: Urea is used to prepare medicine for kala azar or black fever.

Question 16. Why is liquid ammonia used as a coolant?
Answer: Liquid ammonia is used as a coolant due to its high latent heat of vaporisation.

Question 17. State whether the chemical reaction involved in Haber’s process of ammonia synthesis is exothermic or endothermic.
Answer: The chemical reaction involved in Haber’s process of ammonia synthesis is exothermic.

Question 18. Name a promoter which can be used instead of molybdenum (Mo) dust in Haber’s process of ammonia synthesis.
Answer: A mixture of  Al2O3 and K2O can be used as a promoter instead of Mo dust in Haber’s process of ammonia synthesis.

Question 19. Which nitrogenous compound is produced by the hydrolysis of calcium cyanamide?
Answer: Ammonia (NH3) is produced by the hydrolysis of calcium cyanamide.

Question 20. Which gas when passed over heated CuO produces N2 gas?
Answer: Ammonia gas when passed over heated CuO produces N2 gas.

Question 21. By the decomposition of which element, present in the urine of vertebrates, ammonia gas is released?
Answer: Urea.

Question 22. Which gas is termed as alkaline air?
Answer: Ammonia gas is termed as alkaline air.

Question 23. How is ammonia gas collected at laboratory?
Answer: Ammonia gas is collected at laboratory by the downward displacement of air.

Question 24. Name the process by which ammonia gas is prepared commercially.
Answer: Haber’s process.

Question 25. Name a gas which turns the moist red litmus paper blue?
Answer: Ammonia (NH3).

Question 26. Name a gas which forms dense white fumes when it comes in contact to HCI?
Answer: Ammonia (NH3).

Question 27. Which gas is formed by the reaction of ammonia with sodium?
Answer: Hydrogen ( H2)gas is formed by the reaction of ammonia with sodium.

Question 28. Which gas is identified using Nessler’s reagent?
Answer: Ammonia gas.

Question 29. Mention an use of liquid ammonia.
Answer: Liquid ammonia is used as a refrigerant in cold storages or in ice factories.

Question 30. What is liquor ammonia?
Answer:

Liquor ammonia

Concentrated aqueous solution of ammonia (specific gravity = 0.88) is termed as liquor ammonia. In liquor ammonia, almost 35% ammonia is dissolved in water under high pressure.

Question 31. Write down the name and formula of a nitrogenous organic fertiliser.
Answer: Urea (formula H2NCONH2).

Question 32. Write down the conditions for the preparation of urea from ammonia and carbon dioxide.
Answer: Urea is prepared by the reaction of liquid ammonia and carbon dioxide at around 175 atmospheric pressure and at a temperature of 170-190°C.

Question 33. Mention an use of urea.
Answer:

Use of urea

Urea is used as a nitrogenous organic fertiliser.

Inorganic Chemistry In Laboratory And Chemical Industry Topic A Ammonia And Urea Fill In The Blanks

Question 1. Ammonia gas is ______ than air.
Answer: Lighter

Question 2. Anhydrous CaCI2 absorbs ammonia to form an ______ compound.
Answer: Addition

Question 3. Quicklime can be used to dry ammonia gas because it is ______ in nature.
Answer: Basic

Question 4. At normal temperature and pressure _______ mL ammonia gas can dissolve in 1 mL water.
Answer: 1300

Question 5. The reaction between FeCl3 and NH4OH is a ______ reaction.
Answer: Double displacement

Question 6. Concentrated H2SO4 absorbs ammonia to from _____ salt.
Answer: (NH4)2SO4

Question 7. _____ is widely used as a non-aqueous aolvent.
Answer: Liquid ammonia

Question 8. The chemical name of urea is _____
Answer: Carbamide

Question 9. An example of a nitrogenous organic fertiliser is ______
Answer: Urea

Question 10. Ammonia can not be dried up using concentrated H2SO4 as ammonia is an ______ substance.
Answer: Alkaline

Question 11. Optimum temperature and pressure for the preparation of ammonia by Haber’s process is ____ and ______ respectively.
Answer: 450C, 200atm

Question 12. Vapour density of ammonia gas is ______
Answer: 8.5

Question 13. The latent heat of vaporisation of liquid ammonia is very ______
Answer: High

Question 14. The deep blue complex salt formed by dissolving the compound formed by adding ammonia solution in CuSO4 solution in excess NH4OH is ______
Answer: Cu(NH3)4SO4

Inorganic Chemistry In Laboratory And Chemical Industry Topic A Ammonia And Urea State Whether True Or False

Question 1. In the laboratory preparation of ammonia, ammonium chloride and calcium hydroxide are taken in a ratio of 3 :1 by mass.
Answer: False

Question 2. Liquor ammonia contains about 50% of ammonia.
Answer: False

Question 3. The addition compound formed due to the reaction between anhydrous calcium chloride and ammonia is CaCl2 • 10NH3
Answer: False

Question 4. Trace amount of ammonia present in air or water can be detected by its reaction with Nessler’s reagent.
Answer: True

Question 5. The chemical reaction involved in preparation of ammonia by Haber’s process is an endothermic reaction.
Answer: False

Question 6. Urea is used to prepare barbiturates which is a kind of tranquilizer.
Answer: True

Question 7. Ammonia was initially named as ‘alkaline air’ by Priestly.
Answer: True

Question 8. Nessler’s solution turns brown by absorbing ammonia gas.
Answer: True

Question 9. Liquor ammonia is aqueous solution of ammonia.
Answer: True

Question 10. In case of ammonia leakage, you have to give a splash of water in the eyes and all over your face.
Answer: True

Question 11. The required pressure in Haber’s process is 2 atm.
Answer: False

Question 12. Iron dust is used as catalyst in the industrial preparation of ammonia from  N2 and H2.
Answer: True

Question 13. Urea is used to prepare cellophane and rayon.
Answer: True

Question 14. Catalytic oxidation of ammonia produces nitric oxide.
Answer: True

Inorganic Chemistry In Laboratory And Chemical Industry Topic B Hydrogen Sulphide And Nitrogen Synopsis


Laboratory preparation of H2S:
Hydrogen sulphide (H2S) gas is prepared in the laboratory by treating ferrous sulphide with dilute H2SO4 at ordinary temperature. Hydrogen sulphide being heavier than air is collected in a gas jar by upward displacement of air. Kipp’s apparatus is used in the laboratory to get a continuous supply of H2S.

\(\mathrm{FeS}+\mathrm{H}_2 \mathrm{SO}_4 \text { (dil.) } \rightarrow \mathrm{FeSO}_4+\mathrm{H}_2 \mathrm{~S}\)


Properties of H2S:

1. Hydrogen sulphide (H2S) is a colourless, poisonous gas having a smell similar to that of rotten eggs. The poisonous nature of the gas is due to its chemical properties.
2. The aqueous solution of H2S is mildly acidic. It is a strong reducing agent and precipitates metal ions from aqueous solutions of their salts as insoluble sulphides.
3. Freshly prepared alkaline solution of sodium nitroprusside turns violet in the presence of H2S gas. Hence, this reaction can be used for the identification of H2S gas.

Reaction of H2S with blue CuSO4 solution: \(\mathrm{CuSO}_4+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{CuS} \downarrow+\mathrm{H}_2 \mathrm{SO}_4\)
(black)

Reaction of H2S with Pb(NO3)2 solution: \(\mathrm{Pb}\left(\mathrm{NO}_3\right)_2+\mathrm{H}_2 \mathrm{~S} \rightarrow \text { PbS } \downarrow+2 \mathrm{HNO}_3\)
(black)

Reaction of H2S with acidified AgNO3 solution: \(\mathrm{AgNO}_3+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{Ag}_2 \mathrm{~S} \downarrow+2 \mathrm{HNO}_3\)
(black)

Uses of H2S: H2S is used in the preparation of different sulphide and bisulphide salts. It is used as an important laboratory reagent. It works as a precipitating reagent in the qualitative and quantitative analysis of inorganic salts.

Laboratory preparation of N2: In the laboratory, nitrogen gas is prepared by cautiously heating a concentrated aqueous solution of a mixture of sodium nitrite and ammonium chloride. The gas so formed is collected by downward displacement of water.

Step 1: \(\mathrm{NaNO}_2+\mathrm{NH}_4 \mathrm{Cl} \rightarrow \mathrm{NaCl}+\mathrm{NH}_4 \mathrm{NO}_2\)

Step 2: \(\mathrm{NH}_4 \mathrm{NO}_2 \rightarrow \mathrm{N}_2+2 \mathrm{H}_2 \mathrm{O}\)

Physical properties of N2: Nitrogen (N2) is a colourless, odourless and tasteless gas. It is sparingly soluble in water. The boiling point of liquid nitrogen is -195.8°C.

Chemical properties of N2: Nitrogen is chemically inert at normal temperatures. This is due to the high stability of N2 molecule as the two nitrogen atoms are linked to each other by a triple bond. This bond cannot be dissociated by the heat liberated during ordinary chemical reactions. Very high temperature is required to rupture this strong bond.

Reaction of N2 with Mg: N2 reacts with Mg at a very high temperature to form Mg3N2 (magnesium nitride).

\(3 \mathrm{Mg}+\mathrm{N}_2 \rightarrow \mathrm{Mg}_3 \mathrm{~N}_2\)

Reaction of N2 with Calcium carbide: When nitrogen gas is passed over hot calcium carbide (heated at 1100°C), a grey mixture of caicium cyanamide and carbon is formed. This mixture is termed as nitrolim and is used as fertiliser.

\(\mathrm{CaC}_2+\mathrm{N}_2 \stackrel{1100^{\circ} \mathrm{C}}{\longrightarrow} \mathrm{CaNCN}+\mathrm{C}\)
(Nitrolium)

Uses of N2:

1. Nitrogen is used in the preparation of different nitrogenous fertilisers such as ammonium sulphate, ammonium nitrate, urea, nitrolim etc.
2. It is also used for the industrial preparation of NH3 and HNO3.
3. Liquid nitrogen is used as a refrigerant to preserve eye, blood, cornea etc.
4. In laboratories nitrogen is used to create inert environment.

Nitrogen fixation: The conversion of atmospheric nitrogen into several nitrogenous compounds by natural or artificial processes is called nitrogen fixation.

Inorganic Chemistry In Laboratory And Chemical Industry Topic B Hydrogen Sulphide And Nitrogen Short And Long Answer Type Questions

Applications of Inorganic Chemistry in Manufacturing


Question 1. Why is concentrated H2SO4 or anhydrous CaCl or quick lime (CaO) not used to dry H2S gas prepared in the laboratory?

Answer: If concentrated  H2SO4 is used in drying H2S gas, then H2S is oxidised by concentrated  H2SO4 to sulphur. So, concentrated  H2SO4 is,not suitable for drying H2S gas prepared in the laboratory.

\(\mathrm{H}_2 \mathrm{~S}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{S} \downarrow+\mathrm{SO}_2 \uparrow+2 \mathrm{H}_2 \mathrm{O}\)

 

On the other hand, CaCl2 reacts with H2S to form calcium sulphide and liberates hydrogen chloride gas. So, anhydrous CaCl2 is not a suitable drying agent for H2S.

\(\mathrm{CaCl}_2+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{CaS}+2 \mathrm{HCl}\)

 

H2S being an acidic compound reacts with bases such as quick lime to produce calcium sulphide and water. Thus, quick lime cannot be used to dry H2S gas prepared in the laboratory.

\(\mathrm{CaO}+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{CaS}+\mathrm{H}_2 \mathrm{O}\)

 

Question 2. Why does the white colour of objects made of silver or oil paintings slowly turn black?

Answer: Atmospheric air contains traces of H2S. It slowly reacts with silver to form silver sulphide (Ag2S) which forms a black layer over the object made of silver. Hence, the object turns black with time.

\(2 \mathrm{Ag}+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{Ag}_2 \mathrm{~S}+\mathrm{H}_2\)

The white colour of oil paintings contain compounds of lead such as PbCO3, Pb(OH)2 etc. These lead compounds react with H2S present in air to form black lead sulphide (PbS). Hence, the white colour of oil paintings turn black with time.

\(\begin{gathered}
\mathrm{Pb}(\mathrm{OH})_2+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{PbS}+2 \mathrm{H}_2 \mathrm{O} \\
\mathrm{PbCO}_3+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{PbS}+\mathrm{H}_2 \mathrm{CO}_3
\end{gathered}\)


Question 3. Write some of the important uses of H2S.

Answer:

Some important uses of H2S gas are as follows:

1. H2S is used for the preparation of different sulphide and bisulphide salts.
2. It is used as a reducing agent in laboratories.
3. It is also used as a precipitating agent for the qualitative and quantitative analysis of inorganic salts.

Question 4. Discuss the principle of preparation of nitrogen gas in the laboratory along with a suitable equation.

Answer:

The principle of preparation of nitrogen gas in the laboratory along with a suitable equation

Principle: In the laboratory, nitrogen gas is prepared by carefully heating a concentrated aqueous mixture of sodium nitrite and ammonium chloride taken in a 1:1 molar ratio. The reaction takes place in two steps-

1. In the first step, ammonium chloride and sodium nitrite reacts with each other to form ammonium nitrite and sodium chloride.

\(\mathrm{NaNO}_2+\mathrm{NH}_4 \mathrm{Cl} \rightarrow \mathrm{NH}_4 \mathrm{NO}_2+\mathrm{NaCl}\)

 

2. Ammonium nitrite produced in the first step immediately decomposes to produce nitrogen on heating.

WBBSE Solutions For Class 10 Physical Science And Environment Physical And Chemical Properties Of Elements Inorganic Chemistry In Laboratory And Chemical Industry Laboratory Preparation Of Nitrogen

Question 5. Write some important uses of nitrogen.

Answer:

Some important uses of nitrogen are:

1. Nitrogen is used in the industrial preparation of ammonia and nitric acid.
2. It is used in the preparation of nitrogenous fertilisers such as ammonium sulphate, ammonium phosphate, ammonium nitrate, urea, nitrolim etc.
3. It is used to provide inert environment during chemical reactions.
4. Liquid nitrogen is used as a refrigerant to provide very low temperatures.

Question 6. Write with chemical equations what happens when a burning Mg-ribbon is introduced into a gas jar filled with N2 gas and the product thus obtained is boiled with water.

Answer:

When a red hot or a burning Mg-ribbon is introduced into a gas jar filled with dry N2 gas, it burns with a bright flame and magnesium nitride is produced.

\(3 \mathrm{Mg}(s)+\mathrm{N}_2(g) \rightarrow \mathrm{Mg}_3 \mathrm{~N}_2(s)\)

 

When magnesium nitride is boiled with water, it undergoes hydrolysis to produce magnesium hydroxide and liberates pungent-smelling ammonia gas.

\(\begin{array}{r}
\mathrm{Mg}_3 \mathrm{~N}_2(s)+6 \mathrm{H}_2 \mathrm{O}(\mathrm{I}) \rightarrow \\
3 \mathrm{Mg}(\mathrm{OH})_2(a q)+2 \mathrm{NH}_3(g)
\end{array}\)


Question 7. Discuss nitrogen fixation of aerial nitrogen by natural processes, or, Thunderstorms and electric discharge during rainy season are helpful for the plant kingdom—explain.

Answer:

During thunderstorms and electric discharge in the rainy season, atmospheric nitrogen and oxygen combine chemically with each other to form nitric oxide (NO).

\(\mathrm{N}_2+\mathrm{O}_2 \stackrel{\text { electric discharge }}{\longrightarrow} 2 \mathrm{NO}\)

 

This nitric oxide is then oxidised by aerial oxygen to form nitrogen dioxide.

\(2 \mathrm{NO}+\mathrm{O}_2 \rightarrow 2 \mathrm{NO}_2\)

 

NO2 thus formed dissolves in rain water to form nitrous acid (HNO2) and nitric acid (HNO3). These acids fall to the ground with rain water

\(2 \mathrm{NO}_2+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{HNO}_2+\mathrm{HNO}_3\)

 

HNO3 reacts with different basic salts, such as, calcium carbonate, sodium carbonate etc., present in the soil to form water soluble nitrate salts. Plants utilise these nitrate salts for protein synthesis.

Thus, thunderstorms and electric discharge in the rainy season are helpful for the plant kingdom.

Word Problems on Physical and Chemical Properties

Question 8. A colourless, odourless gas A reacts with magnesium to form a compound B. When B is boiled with water, a gas C having strong pungent smell is formed. C produces white fumes of compound D when it comes in contact with a glass rod dipped in HCI. Identify A, B, C and D and write the corresponding equations.

Answer:
A: Nitrogen (N2)
B: Magnesium nitride (Mg3N2)
C: Ammonia (NH3)
D: Ammonium chloride (NH4CI)

Reactions:

\(3 \mathrm{Mg}+\mathrm{N}_2 \rightarrow \mathrm{Mgg}_3 \mathrm{~N}_2\) \(\mathrm{Mg}_3 \mathrm{~N}_2+6 \mathrm{H}_2 \mathrm{O} \rightarrow 3 \mathrm{Mg}(\mathrm{OH})_2+2 \mathrm{NH}_3\) \(\mathrm{NH}_3+\mathrm{HCl} \rightarrow \mathrm{NH}_4 \mathrm{Cl}\)

 

Question 9. State the principle of laboratory preparation of hydrogen sulphide and give Re equation involved.

Answer:
Principle: In the laboratory, hydrogen sulphide is prepared by reacting ferrous sulphide (FeS) with dilute sulphuric acid (H2SO4) at normal temperature.

Chemical equation: \(\mathrm{FeS}(s)+\mathrm{H}_2 \mathrm{SO}_4(l) \rightarrow \mathrm{FeSO}_4(s)+\mathrm{H}_2 \mathrm{~S}(g) \uparrow\)

Question 10. Why is concentrated H2SO4 not used in the laboratory preparation of H2S?

Answer: Concentrated H2SO4 being an oxidising agent oxidises the produced H2S gas to S and itself gets reduced to SO2. Thus, concentrated H2SO4 is not used in the laboratory preparation of H2S.

\(\begin{gathered}
\mathrm{FeS}+\mathrm{H}_2 \mathrm{SO}_4 \text { (conc) } \rightarrow \mathrm{FeSO}_4+\mathrm{H}_2 \mathrm{~S} \uparrow \\
\mathrm{H}_2 \mathrm{~S}+\mathrm{H}_2 \mathrm{SO}_4 \text { (conc) } \rightarrow \mathrm{S} \downarrow+\mathrm{SO}_2 \uparrow+2 \mathrm{H}_2 \mathrm{O}
\end{gathered}\)

 

Question 11. Why is HNO3 not used in the laboratory preparation of H2S?

Answer: HNO3 being an oxidising agent oxidises the produced H2S gas to sulphur and itself gets reduced to  NO2. Hence, HNO3 is not used in the laboratory preparation of H2S.

\(\begin{gathered}
\mathrm{FeS}+2 \mathrm{HNO}_3 \rightarrow \mathrm{Fe}\left(\mathrm{NO}_3\right)_2+\mathrm{H}_2 \mathrm{~S} \\
\mathrm{H}_2 \mathrm{~S}+2 \mathrm{HNO}_3 \rightarrow \mathrm{S} \downarrow+2 \mathrm{NO}_2 \uparrow+2 \mathrm{H}_2 \mathrm{O}
\end{gathered}\)

 

Question 12. What type of gases can be prepared in the Kipp’s apparatus? What is the advantage of using the Kipp’s apparatus?

Answer:

1. The gases which can be produced at room temperature without heating the reactants (such as, CO2, H2, H2S etc.) can be prepared in the Kipp’s apparatus. In case of such gases the reactants start reacting whenever they come in contact to each other. Moreover in order to prepare a gas in Kipp’s apparatus, one of the two reactants must be in liquid phase.

2. The advantage of using the Kipp’s apparatus in the laboratory is that a continuous supply of the gas, prepared in the Kipp’s apparatus, can be conveniently obtained. Moreover by using Kipp’s apparatus a gas can be prepared as per the requirement and the production of the gas can be stopped as soon as the requirement is over.

 

Question 13. Hydrogen sulphide is a toxic gas— explain.

Answer:

Hydrogen sulphide is a toxic gas

Hydrogen sulphide is a colourless toxic gas with a strong smell similar to that of rotten eggs. It causes burning sensation in eyes, headache, nausea etc. On inhaling the gas, one may become unconscious and may even die on prolonged inhalation of the gas.

So, inhaling air containing more than 5 ppm of H2S adversely affects our health. The toxic effect of H2S is basically due to its reaction with the essential proteins of the body cells.

Question 14. Under what conditions, combustion of H2S produces S and SO2 respectively? Give the corresponding chemical equation for each case.

Answer: H2S burns with a blue flame in presence of oxygen or air. Combustion of H2S in limited supply of oxygen produces yellow powder of sulphur. However, in presence of sufficient oxygen, SO2 and water are formed as the products.

\(\begin{aligned}
& 2 \mathrm{H}_2 \mathrm{~S}+\mathrm{O}_2 \text { (insufficient) } \rightarrow 2 \mathrm{~S}+2 \mathrm{H}_2 \mathrm{O} \\
& 2 \mathrm{H}_2 \mathrm{~S}+3 \mathrm{O}_2 \text { (excess) } \rightarrow 2 \mathrm{SO}_2+2 \mathrm{H}_2 \mathrm{O}
\end{aligned}\)

 

Question 15. H2S behaves as a dibasic acid in aqueous medium—explain.

Answer:

H2S behaves as a dibasic acid in aqueous medium

H2S partially ionises in water to produce H + ions. The ionisation takes place in two steps.

\(\mathrm{H}_2 \mathrm{~S} \rightleftharpoons \mathrm{H}^{+}+\mathrm{HS}^{-} ; \mathrm{HS}^{-} \rightleftharpoons \mathrm{H}^{+}+\mathrm{S}^{2-}\)

Hence, it behaves as a dibasic acid in aqueous medium.

In aqueous medium, H2S reacts with a base and produces two different types of salts. For example, when aqueous solution of H2S reacts with NaOH, sodium bisulphide (NaHS) which is an acidic salt and sodium sulphide (Na2S) which is a normal salt are formed.

Question 16. A water sample saturated with H2S gas turns turbid when it is left in the open air for a long period of time. Why?

Answer:

A water sample saturated with H2S gas turns turbid when it is left in the open air for a long period of time.

When a water sample saturated with H2S gas is left in the open air for a long period of time, the dissolved H2S gas is partially oxidised by aerial oxygen to form insoluble sulphur which remains in water as colloidal particles. Consequently the solution turns turbid.

\(2 \mathrm{H}_2 \mathrm{~S}+\mathrm{O}_2 \rightarrow 2 \mathrm{~S} \downarrow+2 \mathrm{H}_2 \mathrm{O}\)

 

Question 17. Give an example of the reducing property of H2S.

Answer:

An example of the reducing property of H2S

When H2S gas is passed through an orange coloured solution of acidified potassium dichromate solution, H2S reduces potassium dichromate to green chromic salt [Cr2(SO4)3] due to which the solution turns green. H2S itself gets oxidised to form sulphur (S).

Question 18. What happens when H2S gas is passed through an aqueous solution of copper sulphate? Give balanced chemical equation.

Answer: When H2S gas is passed through a blue coloured aqueous solution of copper sulphate, a black precipitate of copper sulphide is formed.

\(\mathrm{CuSO}_4+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{CuS} \downarrow+\mathrm{H}_2 \mathrm{SO}_4\)
(blue solution)    (black)


Question 19. What happens when H2S gas is passed through an aqueous solution of lead nitrate? Give balanced chemical equation.

Answer: When H2S gas is passed through a colourless aqueous solution of lead nitrate, a black precipitate of lead sulphide is formed.

\(\mathrm{Pb}\left(\mathrm{NO}_3\right)_2+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{PbS} \downarrow+2 \mathrm{HNO}_3\)
(Colorless solution)    (black)

WBBSE Class 10 Inorganic Chemistry


Question 20. What happens when H2S gas is passed through an aqueous solution of silver nitrate? Give balanced chemical equation.

Answer: When H2S gas is passed through a colourless aqueous solution of silver nitrate, a black precipitate of silver sulphide is formed.

\(2 \mathrm{AgNO}_3+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{Ag}_2 \mathrm{~S} \downarrow+2 \mathrm{HNO}_3\)
(Colourless Solution)     (black)

 

Question 21. Why does a paper soaked in lead acetate solution turn black in presence of H2S gas?

Answer: A paper soaked in lead acetate solution turns black in presence of H2S gas because lead acetate reacts with H2S to form a black precipitate of lead sulphide. As a result, the paper turns black.

\(\mathrm{Pb}\left(\mathrm{CH}_3 \mathrm{COO}\right)_2+\mathrm{H}_2 \mathrm{~S} \rightarrow \underset{\text { (black) }}{\mathrm{PbS} \downarrow}+2 \mathrm{CH}_3 \mathrm{COOH}\)

 

Question 22. How is hydrogen sulphide identified by an alkaline solution of sodium nitroprusside?

Answer: The gas to be identified is passed through an aqueous solution of caustic soda followed by addition of freshly prepared alkaline sodium nitroprusside solution. If the colourless solution turns violet, then it is confirmed that the unknown gas is hydrogen sulphide.

Na2[Fe(CN)5NO] + H2S + 2NaO(H)  → Na4[Fe(CN)5NOS] + 2H2O

Question 23. A black solid A reacts with dilute H2SO4 to produce a gas B having a characteristic smell. When B is passed through acidified potassium dichromate solution, compound C is produced due to which the orange colour of the solution turns green. Identify A, B and C and write the corresponding chemical equations.

Answer:
A: Ferrous sulphide (FeS)
B: Hydrogen sulphide (H2S)
C: Chromic sulphate [Cr2(SO4)3]

Wbbse Class 10 Inorganic Chemistry

Chemical reactions:
1. \(\mathrm{FeS}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{FeSO}_4+\mathrm{H}_2 \mathrm{~S} \uparrow\)

2. K2Cr2O7 + 3H2S + 4H2SO4 → Cr2(SO4)3 + K2SO4 + 3S↓ + 7H2O

Question 24. Nitrogen gas is not produced by directly heating ammonium nitrate. Why?

Answer:

Nitrogen gas is not produced by directly heating ammonium nitrate

Ammonium nitrite is an unstable compound and its thermal decomposition occurs very rapidly. So, if ammonium nitrite is directly heated, explosion may occur due to the high rate of the reaction. In order to avoid this, a saturated solution containing ammonium chloride and sodium nitrite is heated to produce nitrogen.

First step: \(\mathrm{NH}_4 \mathrm{Cl}+\mathrm{NaNO}_2 \rightarrow \mathrm{NaCl}+\mathrm{N}_2 \uparrow+2 \mathrm{H}_2 \mathrm{O}\)

Second step: \(\mathrm{NH}_4 \mathrm{NO}_2 \stackrel{\Delta}{\longrightarrow} \mathrm{N}_2 \uparrow+2 \mathrm{H}_2 \mathrm{O}\)

Question 25. N2 is not Produced by heating a dry mixture of solid NH4CI and NaNO2, rather a saturated aqueous solution of these two substances are taken. Why?

Answer:

N2 is not Produced by heating a dry mixture of solid NH4CI and NaNO2, rather a saturated aqueous solution of these two substances are taken.

Solid NH4CI undergoes sublimation, i.e., it directly converts into its vapour state on heating. So,  N2 is not produced by heating a dry mixture of solid NH4CI and NaN O2. As nitrogen is almost insoluble in water, it is produced by heating a saturated aqueous solution of ammonium chloride and sodium nitrite.

Impact of Inorganic Compounds on the Environment

Question 26. Write some important uses of liquid nitrogen.

Answer:

Some important uses of liquid nitrogen:

Liquid nitrogen can create very low temperatures, even lower than -196°C. This property of liquid nitrogen makes it useful to act as a refrigerant in preserving blood, the cornea of eye etc. Nowadays, it is also used as a refrigerant for storing different food items.

Question 27. Why is nitrogen chemically inert at ordinary temperature?

Answer: In a nitrogen molecule, two adjacent nitrogen atoms are linked to each other by a triple covalent bond which is highly stable in nature: To break such a strong bond, large amount of energy is required which cannot be obtained from chemical reactions occurring at ordinary temperature. So nitrogen does not participate in chemical reactions at ordinary temperature.

Question 28. What happens when nitrogen reacts with oxygen? Give the balanced chemical equation and proper condition of the reaction.

Answer: When a mixture of nitrogen and oxygen is heated around 3000°C in an electric arc, nitric oxide (NO) is obtained as a product. The reaction is reversible and endothermic in nature.

\(\mathrm{N}_2+\mathrm{O}_2 \rightleftharpoons 2 \mathrm{NO}-43.3 \mathrm{kcal}\)

Wbbse Class 10 Inorganic Chemistry

Question 29. What happens when nitrogen reacts with hydrogen? Give the balanced chemical equation and proper condition of the reaction.

Answer: When a mixture of nitrogen and hydrogen is heated at a temperature of about 450°C under 200 atm pressure in presence of iron oxide as catalyst and a mixture of K2O and Al2O3 as promoter, ammonia is produced. The reaction is reversible and exothermic in nature.

\(\mathrm{N}_2+3 \mathrm{H}_2 \rightleftharpoons 2 \mathrm{NH}_3+22.4 \mathrm{kcal}\)

 

Question 30. How is nitrolim prepared?

Answer: When nitrogen gas is passed over calcium carbide heated around 1100°C, a grey mixture of calcium cyanamide (CaNCN) and carbon is obtained. This mixture is known as nitrolim.

\(\mathrm{CaCl}_2(s)+\mathrm{N}_2(g) \rightarrow \underbrace{\operatorname{CaNCN}(s)+\mathrm{C}(s)}_{\text {Nitrolim }}\)

 

Question 31. How does nitrolim act as a fertiliser?

Answer: Nitrolim slowly hydrolyses to form ammonia which gets oxidised to nitrate salts by atmospheric oxygen in presence of bacteria. These nitrate ‘salts are water soluble and are consumed by the roots of plants as food.

\(\mathrm{CaNCN}(s)+3 \mathrm{H}_2 \mathrm{O}(I) \rightarrow \mathrm{CaCO}_3+2 \mathrm{NH}_3(g)\) \(2 \mathrm{NH}_3+2 \mathrm{O}_2 \stackrel{\text { Bacteria }}{\longrightarrow} \mathrm{NH}_4 \mathrm{NO}_3+\mathrm{H}_2 \mathrm{O}\)

 

Question 32. Why is H2S gas collected by downward displacement of hot water instead of downward displacement of cold water?

Answer: H2S gas is soluble in cold water but insoluble in hot water. Moreover H2S is lighter than water. That is why it can be collected by downward displacement of hot water. H2S is 1.2 times heavier than air and due to this it can also be collected in the gas jar by the upward displacement of air.

Question 33. Mention a chemical reaction which shows that H2S gas is acidic in nature.

Answer: H2S forms salt and water by reacting with alkalis which shows that H2S gas is acidic in nature.

\(\begin{aligned}
& \mathrm{H}_2 \mathrm{~S}+\mathrm{NaOH} \rightarrow \mathrm{NaHS}+\mathrm{H}_2 \mathrm{O} \\
& \mathrm{NaHS}+\mathrm{NaOH} \rightarrow \mathrm{Na}_2 \mathrm{~S}+\mathrm{H}_2 \mathrm{O}
\end{aligned}\)

NaHS is the acid salt and Na2S is the neutral salt.

Wbbse Class 10 Inorganic Chemistry

Question 34. Write down the change in colour that takes place when H2S gas is passed through Cu(NO3)2 solution.

Answer: When H2S gas is passed through blue Cu(NO3)2 solution, a black precipitate of copper sulphide (CuS) is obtained.

\(\mathrm{Cu}\left(\mathrm{NO}_3\right)_2+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{CuS} \downarrow+2 \mathrm{HNO}_3\)

 

Question 35. Write down with equation what happens when H2S gas is passed through chlorine water.

Answer: When H2S gas is passed through chlorine water, chlorine is reduced by H2S to produce hydrochloric acid (HCI) and H2S itself gets oxidised to elemental sulphur.

\(\mathrm{H}_2 \mathrm{~S}+\mathrm{Cl}_2 \rightarrow 2 \mathrm{HCl}+\mathrm{S} \downarrow\)

 

Question 36. How would you prove that hydrogen sulphide contains hydrogen?

Answer: A colourless gas is produced when heated copper, lead etc. react with hydrogen sulphide gas. This gas burns in the air with a blue flame and water is produced when it burns in presence of oxygen. Therefore, the colourless gas is nothing but hydrogen. Therefore, it can be said that hydrogen sulphide contains hydrogen.

\(\begin{gathered}
\mathrm{Cu}+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{CuS}+\mathrm{H}_2 \uparrow \\
\mathrm{Pb}+\mathrm{H}_2 \mathrm{~S} \rightarrow \mathrm{PbS}+\mathrm{H}_2 \uparrow \\
2 \mathrm{H}_2+\mathrm{O}_2 \rightarrow 2 \mathrm{H}_2 \mathrm{O}
\end{gathered}\)

 

Question 37. Prove that H2S contains sulphur.

Answer: When a burning splint is inserted in a gas jar containing H2S, the gas starts to burn with a blue flame and the flaming splint gets extinguished. The yellow powder obtained in the gas jar produces a suffocating gas with a smell of gunpowder on burning.

This suffocating gas when passed through orange K2Cr2O7 solution (acidified by dilute H2SO4), colour of the solution turns green. So the suffocating gas is SO2 which is formed by burning of yellow powder.

Therefore the yellow powder is sulphur which is obtained during the combustion of H2S. So it can be concluded that H2S contains sulphur.

\(2 \mathrm{H}_2 \mathrm{~S}+\mathrm{O}_2 \rightarrow 2 \mathrm{H}_2 \mathrm{O}+2 \mathrm{~S} \downarrow\) \(\mathrm{S}+\mathrm{O}_2 \rightarrow \mathrm{SO}_2 \uparrow\)

3 SO2 + K2Cr2O7 + H2SO4 → K2SO4+ Cr2(SO4)3 + H2O

Question 38. How do you Identify H2S by chemical reaction?

Answer:
1. If a paper moistened with lead acetate turns black when it comes in contact with a gas smelt like a rotten egg, it can be said that the gas is definitely hydrogen sulphide.

H2S  + (CH3COO)2Pb → PbS↓ + 2CH3COOH

2. If the freshly prepared alkaline sodium nitroprusside solution turns violet when a gas is passed through it, then the gas can be identified as hydrogen sulphide.

Question 39. Why is a bit of brown fumes observed when the connection between a tram when pantograph and an electric wire gets disconnected?

Answer: A lightning spark is generated when the connection between a tram pentograph and an electric wire gets disconnected. This causes a very high temperature. At this high temperature N2 and O2 present in the atmosphere combine to form nitric oxide (NO). This NO is then oxidised by the oxygen of air to form nitrogen dioxide (NO2) which is brown in colour. As a result brown fumes can be observed.

\(\mathrm{N}_2+\mathrm{O}_2 \rightarrow 2 \mathrm{NO} ; 2 \mathrm{NO}+\mathrm{O}_2 \rightarrow 2 \mathrm{NO}_2\)

 

Question 40. What happens when calcium cyanamide is hydrolysed by extremely hot steam?

Answer: Pungent smelling ammonia gas is evolved when calcium cyanamide is hydrolysed by extremely hot steam.

\(\mathrm{CaCN}_2+3 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{CaCO}_3+2 \mathrm{NH}_3 \uparrow\)


Question 41. How can you identify a gas as nitrogen?

Answer: A burning Mg-ribbon is inserted in a colourless, odourless, non-combustible gas and the Mg- ribbon continues burning with glowing flame. A white powder is obtained as residue. The residue forms pungent smelling ammonia gas on reaction with hot water. Hence the colourless, odourless, non-combustible gas is nothing but nitrogen.

\(\begin{gathered}
3 \mathrm{Mg}+\mathrm{N}_2 \rightarrow \mathrm{Mg}_3 \mathrm{~N}_2 \\
\mathrm{Mg}_3 \mathrm{~N}_2+6 \mathrm{H}_2 \mathrm{O} \rightarrow 3 \mathrm{Mg}(\mathrm{OH})_2+2 \mathrm{NH}_3 \uparrow
\end{gathered}\)

Wbbse Class 10 Lab Preparation Of Ammonia

Question 42. Why is H2 gas used in electric bulb instead of air?

Answer: ln order to create an inert atmosphere nitrogen gas is used in electric bulbs. Air can oxidise the tungsten metal of the filament and as a result the filament will burn. That is why nitrogen gas is used instead of air as nitrogen will not undergo any reaction with the filament, hence the filament will remain intact.

Inorganic Chemistry In Laboratory And Chemical Industry Topic B Hydrogen Sulphide And Nitrogen Very Short Answer Type Questions Choose The Correct Answer

Question 1. Which of the following is used in the laboratory preparation of hydrogen sulphide?

  1. FeSO4 and concentrated  HNO3  
  2. FeS and concentrated  H2SO
  3. FeS and dilute  H2SO
  4. FeSO4 and dilute HNO3  

Answer: 3. FeS and dilute  H2SO

Question 2. Dilute HCr is not used in the laboratory preparation of hydrogen sulphide because,

  1. It is an oxidising agent
  2. It is a reducing agent
  3. It reacts very slowly
  4. It is a volatile substance

Answer: 4. It is a volatile substance

Question 3. In aqueous solution, H2S behaves as a

  1. Weak monobasic acid
  2. Weak dibasic acid
  3. Weak monoacidic base
  4. Strong dibasic acid

Answer: 2. Weak dibasic acid

Wbbse Class 10 Lab Preparation Of Ammonia

Question 4. The aqueous solution of ‘which of the following salts does not produce black precipitate when H2S gas is passed through it?

  1. ZnSO4
  2. CuSO4  
  3. AgNO3
  4. Pb(NO3)2

Answer: 1. ZnSO4

Question 5. Combustion of H2S in inadequate supply of oxygen produces

  1. SO2
  2. H2SO
  3. S
  4. Both 1 and 2

Answer: 3. S

Question 6. If  HNO3 is used in the laboratory preparation of H2S, then the produced H2S gas will get oxidised to

  1. SO2
  2. SO3
  3. H2SO4
  4. S

Answer: 4. S

Question 7. Which of the following solutions turns violet on passing H2S gas through it?

  1. Alkaline sodium nitroprusside
  2. Sodium argentocyanide
  3. Nessler’s reagent
  4. Potassium dichromate solution

Answer: 1. Alkaline sodium nitroprusside

Wbbse Class 10 Lab Preparation Of Ammonia

Question 8. H2S is a poisonous gas, because it

  1. Affects the central nervous system
  2. Decreases the efficiency of lungs
  3. Causes brain haemorrhage
  4. Reacts with the essential proteins of our body

Answer: 4. Reacts with the essential proteins of our body

Question 9. When H2S gas is passed through an acidified solution of potassium dichromate (K2Cr2O7), the solution turns

  1. Yellow
  2. Green
  3. Black
  4. Orange

Answer: 2. Green

Question 10. When H2S gas is passed through an aqueous solution of lead nitrate, the colour of the precipitate formed is

  1. White
  2. Brown
  3. Green
  4. Black

Answer: 4. Black

Question 12. Which of the following compounds N2 gas is trapped?

  1. Gunpowder
  2. Bauxite
  3. Chile saltpetre
  4. Haematite

Answer: 3. Chile saltpetre

Question 13. Nitrogen is fixed in the soil as

  1. N2  
  2. NH3
  3. Metallic nitrates
  4. None of these

Answer: 3. Metallic nitrates

Wbbse Class 10 Lab Preparation Of Ammonia

Question 14. Which of the following gases is not prepared in Kipp’s apparatus?

  1. CO2
  2. H2
  3. O2
  4. H2S

Answer: 3. O2

Question 15. Which of the following gas is collected by the downward displacement of water?

  1. NH3
  2. H2S
  3. N2
  4. HCl(g)

Answer: 3. N2

Question 16. Nitrolim is used as a

  1. Fertiliser
  2. Explosive
  3. Medicine
  4. None of these

Answer: 1. Fertiliser

Question 17. Which of the following gases can not be identified by its colour?

  1. CI2
  2. NO2
  3. H2S
  4. None of these

Answer: 3. H2S

Question 18. Which of the following gases is used to detect the basic radicals present in a salt in laboratory?

  1. CO2
  2. N
  3. H2
  4. H2S

Answer: 4. H2S

Question 19. Which of the following gases can be prepared by using Kipp’s apratus?

  1. N
  2. H2S
  3. HCl
  4. NH3

Answer: 2. H2S

Question 20. Which of the following gases has a brown colour?

  1. NO
  2. N2O3
  3. N2O
  4. NO2

Answer: 4. NO2

Question 21. H2S burns with a flame of which colour?

  1. Green
  2. Yellow
  3. Red
  4. Blue

Answer: 4. Blue

Question 22. Which of the following is used to dry moist H2S?

  1. H2SO4(conc.)
  2. H2SO4 (dilute)
  3. P2O5
  4. Anhydrous CaCI2  

Answer: 3. P2O5

Wbbse Class 10 Lab Preparation Of Ammonia

Question 23. In order to remove acid vapour, H2S gas is passed through

  1. HCI (dilute)
  2. H2SO (dilute)
  3. NaOH solution
  4. NaHS solution

Answer: 4. NaHS solution

Question 24. Which of the following gases is heavier than air?

  1. H2S
  2. NH
  3. N2
  4. All of the above

Answer: 1. H2S

Question 25. Which of the following is formed when nitrogen is passed over heated CaC2?

  1. CaCN2
  2. Ca(CN)2
  3. CaCN
  4. Ca2CN

Answer: 1. CaCN2

Question 26. Which of the following is used to prepare nitrogen in laboratory?

  1. NH4CI and CaO.
  2. NH4OH and HNO3
  3. NH3 and NaNO2
  4. NH4CI and NaNO2

Answer: 4. NH4CI and NaNO2

Question 27. Which of the following is used to preserve eye-cornea?

  1. NO
  2. H2S
  3. N2
  4. NO2

Answer: 3. N2

Question 28. Ag turns black in contact with which gas?

  1. HNO3 vapour
  2. NH3 vapour
  3. H2S vapour
  4. H2SO4 vapour

Answer: 3. H2S vapour

Question 29. In the first step of nitrogen fixation, which of the following gases is prepared through lightning?

  1. NO
  2. NO2
  3. N2O5
  4. HNO3  

Answer: 1. NO

Inorganic Chemistry In Laboratory And Chemical Industry Topic B Hydrogen Sulphide And Nitrogen Answer In Brief

Question 1. Write the formula of hydrosulphuric acid.
Answer: The formula of hydrosulphuric acid is H2S.

Question 2. Name the types of salts produced by H2S.
Answer: H2S   can produce two types of salts – acid salts like NaHS and neutral salts like  Na2S.

Question 3. What happens when H2S gas is passed through an alkaline solution of sodium nitroprusside?
Answer: When H2S gas is passed through an alkaline solution of sodium nitroprusside, the solution turns violet.

Question 4. Why does an orange solution of acidified potassium dichromate turns green when H2S gas is passed through it?
Answer: When H2S gas is passed through an orange solution of acidified potassium dichromate K2Cr2O7, the later is reduced by H2S to form green coloured chromic sulphate [Cr2(SO4)].

Question 5. Under what conditions does H2S undergo combustion to produce powdered sulphur?
Answer: H2S undergoes combustion in limited supply of air (oxygen) to produce powdered sulphur.

Question 6. Name the only stable hydride of sulphur.
Answer: The only stable hydride of sulphur is hydrogen sulphide (H2S).

Question 7. In the laboratory preparation of nitrogen, the first step is the formation of NH4NO2. Which type of reaction is this?
Answer: It is a double decomposition reaction.

Question 8. State the temperature at which calcium carbide reacts with N2 to produce nitrolim.
Answer: At 1100°C calcium carbide reacts with nitrogen to produce nitrolim.

Question 9. During lightning, which compound is formed due to the reaction between atmospheric N2   and O2?
Answer: During lightning, atmospheric N2 and O2 react with each other to form nitric oxide

Question 10. Name two major gases that play a vital role in acid production.
Answer: Nitrogen (N2) and oxygen (O2) are the major gases that play a vital role in acid production.

Question 11. Using which apparatus one can get H2S gas as and when required?
Answer: Kipp’s apparatus is used to get H2S gas as and when required.

Question 12. Smell of which gas can be sensed from black salt?
Answer:  H2S gas.

Question 13. How does H2S gas smell like?
Answer: H2S gas smells like rotten egg.

Question 14. Is H2S gas heavier than air or lighter than air?
Answer: H2S gas is heavier than air.

Question 15. What is the colour of the flame when H2S burns in the air?
Answer: H2S burns in the air with a blue flame.

Question 16. Name a gas which is reducing as well as acidic in nature.
Answer: Hydrogen sulphide (H2S) gas.

Question 17. Write down the formula of the black precipitate formed by passing H2S gas through lead nitrate solution.
Answer: Lead sulphide (PbS).

Question 18. Old oil paintings turn black on contact with which gas of air?
Answer: Hydrogen sulphide (H2S) gas.

Question 19. Write down the name and colour of the precipitate obtained by passing H2S through AgNO3 solution.
Answer: Black precipate of silver sulphide (Ag2S) is formed.

Question 20. Why do nickel or silver substances gradually turn black?
Answer: H2S, present in air reacts very slowly with nickel or silver present in these substances and forms corresponding metallic sulphides which are black in colour. This metallic sulphides form a coating on the substances. As a result they turn black.

Question 21. Solution of which substance is mixed with aqueous solution of ammonium chloride and heated to form nitrogen at laboratory?
Answer: Aqueous solution of sodium nitrite.

Question 22. Write down the boiling point of nitrogen.
Answer: Boiling point of nitrogen is -195.8°C .

Question 23. How can ammonia and nitrogen gas be distinguished by their physical properties?
Answer: Ammonia gas is pungent smelling while nitrogen gas is odourless. So by this physical property these two gases can be distinguished.

Question 24. Write down the name of the product formed by the reaction of nitrogen gas with magnesium at high temperature.
Answer: Magnesium nitride.(Mg3N2).

Question 25. Which gas can be obtained by hydrolysis of calcium cyanamide?
Answer: Ammonia (NH3)

Question 26. What is nitrolim?
Answer: The grey mixture of calcium cyanamide and carbon.

Question 27. Write down the use of nitrolim.
Answer: Nitrolim is used as a fertiliser.

Question 28. Which gas is used in gas thermometer?
Answer: Nitrogen gas.

Question 29. Mention the use of liquid nitrogen.
Answer: Liquid nitrogen is used as refrigerant to preserve cornea, eye and blood.

Inorganic Chemistry In Laboratory And Chemical Industry Topic B Hydrogen Sulphide And Nitrogen Fill In The Blanks

 

Question 1. H2S gas can be dried by using _______ as the dehydrating agent.
Answer: P2O5

Question 2. The poisonous nature of H2S is related to its ______ property.
Answer: Chemical

Question 3. The sulphide compound used in the laboratory preparation of H2S is ______
Answer: FeS

Question 4. The acid which cannot be used in the laboratory preparation of H2S is ______
Answer: HNO3

Question 5. H2S being ______ in nature cannot be dried using _____ dehydrating agents.
Answer: Acidic, alkaline

Question 6. H2S gas is _____ than air.
Answer: Heavier

Question 7. The basicity of hydrogen sulphide is ______
Answer: 2

Question 8. H2S is ______ in cold water but _____ in hot water.
Answer: Soluble, insoluble

Question 9. H2S itself is a ______ substance but does not combustion.
Answer: Compustible, support

Question 10. Zinc sulphide is _____ in colour but silver sulphide is ______ in colour.
Answer: White, black

Question 11. H2S gas is identified by using alkaline _______ solution.
Answer: Sodium nitroprusside

Question 12. Magnesium nitride reacts with hot water to produce _____
Answer: Ammonia

Question 13. Nitric acid forms ______ salts while react with the alkaline substances present in the soil.
Answer: Nitrate

Question 14. Solubility of nitrogen in water is very _____
Answer: Low

Question 15. N2 itself is _____ and _____ supprt combustion.
Answer: Incombustible

Question 16. The grey mixture of ______ And carbon is known as nitrolim.
Answer: Calcium cyanamide

Question 17. When metal nitrides are boiled with water the smell of _______ gas is found.
Answer: Ammonia

Question 18. Vapour density of H2S is ______
Answer: 17

Question 19. ______ is formed by combustion of H2S in excess air.
Answer: SO2

Question 20. The antidote of H2S toxicity is dilute ______ solution.
Answer: Chlorine

Question 21. Formula of neither is ______
Answer: KNO3

Question 22. The formed N2 gas is passed through cone, ______ solution to free form moisture.
Answer: H2SO

Question 23. N2 gas is ______ at normal temperature.
Answer: Inert

Question 24. A stable covalent _____ bond is present between two N-atoms of nitrogen molecule.
Answer: Triple

Inorganic Chemistry In Laboratory And Chemical Industry Topic B Hydrogen Sulphide And Nitrogen State Whether True Or False

 

Question 1. Hydrogen sulphide reacts with sodium hydroxide to form sodium sulphide only.
Answer: False

Question 2. Hydrogen sulphide gas itself is a combustible substance but not a supporter of combustion.
Answer: True

Question 3. H2S gas reacts with a colourless aqueous solution of silver nitrate to form a black precipitate of silver sulphide.
Answer: True

Question 4. Kipp’s apparatus is used for the preparation of those gases which are prepared in the laboratory by heating the reactants.
Answer: False

Question 5. At ordinary temperature, nitrogen is chemically very reactive due to the presence of triple bond.
Answer: False

Question 6. In order to remove chlorine, present as impurity, from nitrogen gas prepared in the laboratory,  N2 is passed through concentrated caustic soda solution.
Answer: True

Question 7. Nitrogen gas is adsorbed by active charcoal.
Answer: True

Question 8. Concentrated H2SO4 is used in the laboratory to prepare hydrogen sulphide gas.
Answer: False

Question 9. Old oil paintings turn black in presence of ammonia gas.
Answer: False

Question 10. Components of nitrolim are CaC2 and C.
Answer: False

Question 11. Nitrolim is used as a pesticide in agricultural field.
Answer: False

Inorganic Chemistry In Laboratory And Chemical Industry Topic C [Industrial preparation of HCI, HNO3 and H2SO4] Synopsis

 

Industrial preparation of HCI: Hydrogen chloride gas is produced by the combustion , of equal volumes of H2 and Cl2 gas in a chamber made of silica. The produced gas is cooled and is then dissolved in water to form a saturated solution of hydrochloric acid.

\(\mathrm{H}_2+\mathrm{Cl}_2 \rightarrow 2 \mathrm{HCl}\)


Industrial preparation of HNO3:
Nitric acid is industrially manufactured by Ostwald’s process. In this process, nitric oxide (NO) is produced by catalytic oxidation of ammonia in the presence of aerial oxygen at 700-800°C temperature and 5-7 atm pressure. NO thus obtained is oxidised to form  NO2 gas and it is then dissolved in water to produce  HNO3

Step 1: \(4 \mathrm{NH}_3+5 \mathrm{O}_2 \frac{\mathrm{Pt} \text { (catalyst) }}{5-7 \mathrm{~atm}, 700-800^{\circ} \mathrm{C}} 4 \mathrm{NO}+6 \mathrm{H}_2 \mathrm{O}\)

Step 2: \(2 \mathrm{NO}+\mathrm{O}_2 \rightarrow 2 \mathrm{NO}_2\)

Step 3: \(3 \mathrm{NO}_2+\mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{HNO}_3+\mathrm{NO}\)

Industrial preparation of H2SO4: The industrial preparation of sulphuric acid is carried out by the contact process. In the first step, elemental sulphur or iron pyrites (FeS2) is burnt in air to produce SO2 which is then oxidised to SO3 by aerial oxygen in the presence of V2O5 or platinised asbestos catalyst.

SO3 thus obtained in the second step is absorbed by 98% concentrated H2SO4 to produce oleum (H2S2O7). Oleum is then diluted by adding required amount of distilled water to produce 98% concentrated H2SO4.

Step 1: \(\begin{aligned}
& 4 \mathrm{FeS}_2+11 \mathrm{O}_2 \rightarrow 2 \mathrm{Fe}_2 \mathrm{O}_3+8 \mathrm{SO}_2 \\
& \mathrm{~S}+\mathrm{O}_2 \rightarrow \mathrm{SO}_2
\end{aligned}\)

Step 2: \(2 \mathrm{SO}_2+\mathrm{O}_2 \rightleftharpoons 2 \mathrm{SO}_3+\text { heat }\)

Step 3: \(\begin{aligned}
& \mathrm{H}_2 \mathrm{SO}_4+\mathrm{SO}_3 \rightarrow \mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_7 \text { (oleum) } \\
& \mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_7+\mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{H}_2 \mathrm{SO}_4
\end{aligned}\)

 

Inorganic Chemistry In Laboratory And Chemical Industry Topic C [Industrial preparation of HCI, HNO3 and H2SO4] Short And Long Answer Type Questions

Question 1. Describe briefly the industrial preparation of hydrochloric acid.

Answer:

The industrial preparation of hydrochloric acid:

Nowadays hydrochloric acid is commercially prepared by modern synthetic method. The major steps of the method are discussed below—

1. Almost equal volumes of hydrogen gas and chlorine gas are taken in a combustion chamber made up of silica. When this mixture silica made is combusted hydrogen and chlorine combine with each other to form HCI gas.

\(\mathrm{H}_2(g)+\mathrm{Cl}_2(g) \rightarrow 2 \mathrm{HCl}(g)\)

 

2. The produced hydrogen chloride is cooled by passing it through a coiled tube within a condenser.
3. The condensed gas is then absorbed in water to produce a saturated solution of hydrochloric acid.

Question 2. Describe the principle of industrial Ipreparation of nitric acid by Ostwald’s process and give the corresponding chemical equations.

Answer: The steps involved in the Ostwald’s process are as follows—

First step: A mixture of pure and dry ammonia and dust-free air taken in a ratio of 1: 7.5 by volume is rapidly passed over Pt or a Pt-Rh wire gauze (which acts as a catalyst) at 800-900°C under 5-7 atm pressure.

The time of contact between the gas mixture and the catalyst should not be more than 0.0014 sec. As a result, ammonia is oxidised by aerial oxygen to produce nitric oxide (NO). The reaction is reversible and exothermic in nature.

\(\begin{aligned}
4 \mathrm{NH}_3(g)+5 \mathrm{O}_2(g) \rightleftharpoons 4 \mathrm{NO}(g) & +6 \mathrm{H}_2 \mathrm{O}(g) \\
& +216 \mathrm{kcal}
\end{aligned}\)

Second step: NO gas thus obtained is cooled (by bringing the temperature down to 50°C) and is then oxidised by aerial oxygen to form nitrogen dioxide (NO2).

\(2 \mathrm{NO}(g)+\mathrm{O}_2(g) \rightleftharpoons 2 \mathrm{NO}_2(g)+27.2 \mathrm{kcal}\)

Third step: NO2 gas thus produced is dissolved in water to produce 50% nitric acid. It is then heated to 120°C and distilled with concentrated H2SO4 to obtain 98% HNO3.

\(3 \mathrm{NO}_2(g)+\mathrm{H}_2 \mathrm{O}(l) \rightleftharpoons 2 \mathrm{HNO}_3(a q)+\mathrm{NO}(g)\)

Visual Representation of Chemical Reactions in Inorganic Chemistry

 

WBBSE Solutions For Class 10 Physical Science And Environment Physical And Chemical Properties Of Elements Inorganic Chemistry In Laboratory And Chemical Industry Inustrial Preparation Of HNO3

NO gas evolved in this step can be reused ti prepare nitric acid.

Question 3. Discuss the principle of industrial preparation of sulphuric acid by contact process and give the corresponding chemical equation for each step.

Answer: The industrial preparation of sulphuric acid by contact process is as follows—

1. Elementary sulphur or iron pyrites (FeS2) is burnt in excess air to produce SO2.

\(\mathrm{S}(s)+\mathrm{O}_2(g) \rightarrow \mathrm{SO}_2(g)\)

 

4FeS2(s) + 11O2 (g) → 2Fe2O3(s) + 8 SO2(g)

2.  SO2 gas is then purified and mixed with excess amount of pure and dust-free air. It is then heated around 450°C under 1.5 atm pressure and passed over platinised asbestos . or vanadium pentoxide (V2O5) catalyst. Consequently,  SO2 is oxidised by aerial oxygen to form sulphur trioxide ( SO3). The reaction is reversible & exothermic in nature.

\(2 \mathrm{SO}_2(g)+\mathrm{O}_2(g) \rightleftharpoons 2 \mathrm{SO}_3(g)+45 \mathrm{kcal}\)

 

3.  SO3 gas thus produced is then cooled and passed through the absorption tower filled with coke pieces. Here, it gets absorbed in 98% H2SO4 and oleum or pyrosulphuric acid (H2S2O7) is obtained as the product. It is collected in a tank coated with lead.

\(\mathrm{H}_2 \mathrm{SO}_4(l)+\mathrm{SO}_3(g) \rightarrow \mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_7(l)\)

 

4. Finally, proportionate amount of distilled water is added to oleum to produce 98% concentrated sulphuric acid.

\(\mathrm{H}_2 \mathrm{~S}_2 \mathrm{O}_7(l)+\mathrm{H}_2 \mathrm{O}(l) \rightarrow 2 \mathrm{H}_2 \mathrm{SO}_4(l)\)

 

WBBSE Solutions For Class 10 Physical Science And Environment Physical And Chemical Properties Of Elements Inorganic Chemistry In Laboratory And Chemical Industry Industrial Preparation Of H2SO4

Question 4. Why is SO3 not directly dissolved into water during industrial preparation of H2SO4 by contact process?

Answer:
1. Dissolution of  SO in water is a very rapid and exothermic process. Consequently, it leads to an increase in temperature due to which the solubility of  SO in water decreases and most of  SO gas, instead of getting absorbed by water, comes out of the absorption tower.
2. At such a high temperature, water vapour and H2SO4 droplets form a kind of dense white mist which does not easily condense into liquid and causes various problems.
3. Due to the generation of large amount of heat, H2SO4 produced partially decomposes to S03 and oxygen. Hence, production of H2SO4 gets reduced.

Question 5. Why are the catalysts used in the industrial preparation of ammonia, sulphuric acid or nitric acid taken in powdered form?

Answer: In all the cases, gaseous reactants react in presence of solid catalysts. Catalysts are taken in their powdered form in order to increase their surface area. When gases react in the presence of a solid catalyst, the gas molecules are adsorbed on the surface of the catalyst.

This increases the probability of effective collisions among the reactant molecules and hence, the rate of reaction increases. Greater the surface area of the catalyst, greater will be the number of adsorbed reactant molecules on the surface of the catalyst and hence the reaction will take place at a faster rate.

Question 6. Why should the mixture of ammonia and air used for the preparation of nitric acid by Ostwald’s process be pure and dust free?

Answer: In Ostwald’s process, platinum is used as the catalyst which is very expensive. If the mixture of air and ammonia is contaminated with dust, then the dust particles accumulate on the surface of the catalyst, thereby reducing its efficiency. Thus, the dust as well as impurities act as catalyst poison in this case.

Question 7. Why is the mixture of ammonia and air rapidly passed over platinum gauze catalyst for the preparation of nitric acid by Ostwald’s process?

Answer: The mixture of ammonia and air is rapidly passed over Pt-gauze catalyst for the preparation of nitric acid by Ostwald’s process. This is because the time of contact between the reactant mixture and the catalyst should not be longer than 0.0014 seconds. If the time of exposure exceeds this limit, then ammonia gets oxidised to form nitrogen instead of forming NO.

\(4 \mathrm{NH}_3+3 \mathrm{O}_2 \rightarrow 2 \mathrm{~N}_2+6 \mathrm{H}_2 \mathrm{O}\)

 

Question 8. How can we concentrate the dilute nitric acid produced by Ostwald’s method?

Answer: The dilute nitric acid (almost 50%) produced by Ostwald’s process can be first concentrated by heating it to 120°C. First of all it is concentrated up to 68% (by mass) on distillation. Then this acid is concentrated by performing distillation in . presence of concentrated H2SO4 to produce 98%  HNO3.

Question 9. Name the substance which is used as the catalyst in the contact process for manufacturing H2SO4. Why is the process so named?

Answer: Any one of the given compounds can be used as the catalyst in the contact process for manufacture of H2SO4:
1. Platinised asbestos or
2. vanadium pentoxide (V2O5).

As the reactants react with each other in contact with the solid surface of the catalyst, the process for the industrial preparation of H2SO4 is called contact process.

Question 10. Why is V2O5 preferably used as the catalyst in contact process?

Answer: Even though platinised asbestos is more efficient than  V2O5 as a catalyst, the efficiency of the former decreases considerably in presence of even trace amount of impurities. On the other hand,  V2O5 is cheaper and has less chance of getting contaminated in presence of impurities. Hence,  V2O5 is preferably used as the catalyst in the contact process.

Question 11. Why is the mixture of SO2 and Oused in the preparation of sulphuric acid by . icontact process, needed to be free of dust and impurities?

Answer: The mixture of SO2 and Oused for the preparation of sulphuric acid by contact process is needed to be free of dust and impurities (mainly arsenious oxide) because there are several impurities which can act as catalyst poison and reduce the efficiency of the catalyst.

Question 12. Why is the mixture of NO and O2 gases being cooled before passing through oxidation chamber?

Answer: In Ostwald process, the mixture of NO and O2 gases is being cooled before passing through the oxidation chamber. The main objective of this measure is’ to reduce the probability of decomposition of the nitrogen dioxide (NO2) which is to be formed by the reaction of NO and O2 in the oxidation chamber.

Question 13. What is the advantage of being exothermic in nature of the catalytic oxidation of ammonia in Ostwald process.

Answer: In Ostwald process the catalytic oxidation of ammonia is an exothermic process, so there is no need to heat the oxidation chamber once the oxidation reaction has started. Hence the fuel for heating the oxidation chamber is thus saved.

Physical Science Class 10 West Bengal Board

Question 14. Convert: Iron pyrites to sulphur dioxide.

Answer: Iron pyrites can be converted to sulphur dioxide by burning it in excess air.

\(4 \mathrm{FeS}_2+11 \mathrm{O}_2 \rightarrow 2 \mathrm{Fe}_2 \mathrm{O}_3+8 \mathrm{SO}_2 \uparrow\)


Question 15. What is oleum?

Answer: Pyrosulphuric acid is commonly known as oleum. It is a light yellow oily liquid with the chemical formula of H2S2O7. It is also known as fuming sulphuric acid. When sulphur trioxide is absorbed by 98% concentrated sulphuric acid, oleum is obtained.

Inorganic Chemistry In Laboratory And Chemical Industry Topic C [Industrial preparation of HCI, HNO3 and H2SO4] Very Short Answer Type Questions Choose The Correct Answer

 

Question 1. Which of the following reactions is endothermic?

  1. \(\mathrm{N}_2+3 \mathrm{H}_2 \rightarrow 2 \mathrm{NH}_3\)
  2. \(\mathrm{N}_2+\mathrm{O}_2 \rightarrow 2 \mathrm{NO}\)
  3. \(4 \mathrm{NH}_3+5 \mathrm{O}_2 \rightarrow 4 \mathrm{NO}+6 \mathrm{H}_2 \mathrm{O}\)
  4. \(2 \mathrm{SO}_2+\mathrm{O}_2 \rightarrow 2 \mathrm{SO}_3\)

Answer: 2. \(\mathrm{N}_2+\mathrm{O}_2 \rightarrow 2 \mathrm{NO}\)

Question 2. Which of the following acids reacts with skin proteins to form xanthoproteic acid?

  1. Sulphuric acid
  2. Hydrochloric acid
  3. Nitric acid
  4. Nitrous acid

Answer: 3. Nitric acid

Physical Science Class 10 West Bengal Board

Question 3. Which of the following compounds is commercially manufactured by Leblanc process?

  1. Nitric acid
  2. Ammonia
  3. Sulphuric acid
  4. Soda ash

Answer: 4. Soda ash

Question 4. In Leblanc process, the gas produced as a by-product in the first step is

  1. HCI
  2. SO2
  3. NH3
  4. H2S

Answer: 1. HCI

Question 5. The formula of pyrosulphuric acid is

  1. H2S2O8
  2. H2S2O6
  3. H2S2O7
  4. H2S2O5

Answer: 3. H2S2O7

Question 6. The type of reaction involved in the industrial preparation of hydrochloric acid is

  1. Synthesis reaction
  2. Substitution reaction
  3. Double decomposition reaction
  4. Decomposition reaction

Answer: 1. Synthesis reaction

Physical Science Class 10 West Bengal Board

Question 7. In the industrial preparation of nitric acid by Ostwald’s process, the catalyst used is

  1. Ni
  2. Pt
  3. Fe
  4. Cu

Answer: 2. Pt

Question 8. The starting materials used in the industrial preparation of nitric acid by Ostwald’s process are

  1. N2 and O2
  2. NO and O2
  3. NH3 and O2
  4. N2O and O2

Answer: 3. NH3 and O2

Question 9. Optimum temperature for the 1st step of the Ostwald process of HNO3 preparation is

  1. 400°C-500°C
  2. 600°C-700°C
  3. 700°C-800°C
  4. 1000°C-1200°C

Answer: 3. 700°C-800°C

Question 10. The catalyst used in the contact process of H2SO4 preparation

  1. Platinised asbestos
  2. V2O5         
  3. Ni-dust
  4. 1 or 2

Answer: 4. 1 or 2

Question 11. In which of the following phases, efficiency of the solid catalyst increases?

  1. Solid particle
  2. Fused state
  3. Dust
  4. None of the above

Answer: 3. Dust

Physical Science Class 10 West Bengal Board

Question 12. The optimum temperature of the contact process for H2SO4 preparation

  1. 623°C
  2. 623K
  3. 723°C
  4. 723K

Answer: 4. 723K

Question 13. Which of the following acid is known as ‘oil of vitriol’?

  1. HNO3
  2. H2SO4
  3. HCI
  4. HBr

Answer: 2. H2SO4

Question 14. The oxide formed by catalytic oxidation of ammonia for the industrial preparation of nitric acid

  1. NO2
  2. N2O4
  3. N2O5
  4. NO

Answer: 4. NO

Inorganic Chemistry In Laboratory And Chemical Industry Topic C [Industrial preparation of HCI, HNO3 and H2SO4] Answer In Brief

 

Question 1. Name the industrial process by which nitric acid is prepared from ammonia.
Answer: Industrially nitric acid is prepared from ammonia by Ostwald’s process.

Question 2. HCI gas produces white fumes in moist air. Why?
Answer: HCI gas combines with water vapour to form tiny particles of acid which float in air producing white fumes.

Question 3. What happens when a mixture of ammonia and air is passed over heated platinum?
Answer: When a mixture of ammonia and air is passed over heated platinum, nitric oxide (NO) and water vapour are formed.

Question 4. Which acids are produced when NO2 gas is absorbed in water?
Answer: When NO2 gas is absorbed in water, nitric acid (HNO3) and nitrous acid (HNO2) are formed.

Question 5. Name the process for the industrial preparation of H2SO4.
Answer: Contact process is used for the industrial preparation of H2SO4.

Question 6. In the industrial preparation of H2SO4, which mineral of iron undergoes combustion in air to produce  SO2?
Answer: In the industrial preparation of H2SO4, iron pyrites (FeS2) undergoes combustion in air to produce  SO2.

Physical Science Class 10 West Bengal Board

Question 7. What is the chemical formula of fuming sulphuric acid or oleum?
Answer: The chemical formula of fuming sulphuric acid or oleum is H2S2O7.

Question 8. In what form catalysts are usually used in the industrial preparations of different compounds?
Answer: During industrial preparations of different compounds, catalysts are usually used in their powdered form.

Question 9. Which inorganic acid is secreted in the stomach?
Answer: Hydrochloric acid (HCI).

Question 10. Write down the formula of muriatic acid?
Answer: Formula of muriatic acid is HCI.

Question 11. Which gas is evolved in the reaction of common salt with concentrated H2SO4?
Answer: Steamy fumes of hydrogen chloride (HCI) gas is evolved.

Question 12. Write down the formula of ‘aquafortis’?
Answer: Formula of ‘aqua fortis’ is HNO3 .

Question 13. Name the industrial process for the preparation of nitric acid from ammonia.
Answer: Ostwald process.

Question 14. Which catalyst is used in the conversion of SO2 to SO3 in contact process?
Answer: Vanadium pentoxide (V2O5).

Question 15. Write down one use of oleum.
Answer: Oleum is used as a reagent (especially in organic reactions) in chemical laboratory.

Question 16. What is sulphan?
Answer:

Sulphan

Sulphan is 100% oleum. In other words sulphan or oleum is a mixture of concentrated sulphuric acid that has been saturated with excess sulphur trioxide.

Inorganic Chemistry In Laboratory And Chemical Industry Topic C [Industrial preparation of HCI, HNO3 and H2SO4] Fill In The Blanks

 

Question 1. When an electric spark is passed through a mixture of Nand O2 at 3000°C, ______ is formed as the product.
Answer: NO

Physical Science Class 10 West Bengal Board

Question 2. In the industrial preparation of HNO3 by Ostwald’s process, ammonia is first oxidised to _____
Answer: NO

Question 3. The chemical name of fuming sulphuric acid is ______
Answer: Pyrosulphuric acid

Question 4. ______ is mixed with fuming sulphuric acid to produce sulphuric acid solution.
Answer: Water

Question 5. _______ gas is formed by the combustion of the mixture of equal volume of H2 and CI2 gas.
Answer: HCl

Question 6. ______ is used as catalyst in the industrial preparation of HNO3 by Ostwald process.
Answer: Platinum

Question 7. ________ acid is prepared by contact process.
Answer: Sulphuric

Question 8. The conversion of SO2 to SO3 by contact process is ______ and _______ is nature.
Answer: Reversible, exthermic

Question 9. The formula of pyrosulfuric acid is ______
Answer: H2S2O7

Inorganic Chemistry In Laboratory And Chemical Industry Topic C [Industrial preparation of HCI, HNO3 and H2SO4] State Whether True Or False

 

Question 1. The anhydride of nitric acid is nitrogen pentoxide (N2O5).
Answer: True

Question 2. The oxidation of SO2 to SO3 in the contact process is carried out at a temperature of 450°C under 1.5 atm pressure.
Answer: True

Question 3. The first step of the contact process involves reduction of iron pyrites to form sulphur dioxide.
Answer: False

Physical Science Class 10 West Bengal Board

Question 4. The industrial preparation of HCI involves combustion of a mixture of equal volumes of hydrogen and chlorine gases.
Answer: True

Question 5. In contact process of H2SO4 preparation, SO3 is directly dissolved in water to form sulphuric acid.
Answer: False

Question 6. Greater the surface area of a catalyst, higher will be the number of reactant molecules adsorbed on the surface of the catalyst.
Answer: True

Question 7. If the contact time between reactants and the catalyst becomes longer in the first step of the Ostwald’s process then nitrogen is formed by incomplete oxidation of ammonia.
Answer: True

Question 8. HCI is obtained as a byproduct in the first step of Leblanc process.
Answer: True

Inorganic Chemistry In Laboratory And Chemical Industry Miscellaneous Type Questions Match The Column

 

Question 1.

Column A Column B
NH4CI and Ca(OH)2 1. Laboratory preparation of hydrogen sulphide
FeS and dil. H2SO4 2. Industrial preparation of urea
NH4CI and NaNO2 3. Laboratory preparation of ammonia
NH3 + CO2 4. Laboratory preparation of nitrogen

 

Answer:
NH4CI and Ca(OH)2: 3. Laboratory preparation of ammonia
FeS and dil. H2SO4: 1. Laboratory preparation of hydrogen sulphide
NH4CI and NaNO2: 4. Laboratory preparation of nitrogen
NH3 + CO2: 2. Industrial preparation of urea

Question 2.

Column A Column B
Pyrosulphu-ric acid 1. Chemical name of urea
Smelling salt 2. Mixture of calcium cyanamide and carbon
Nitrolim 3. A mixture of ammonium carbonate and lime water
Carbamide 4. Oleum

 

Answer:
Pyrosulphu-ric acid: 4. Oleum
Smelling salt: 2. Mixture of calcium cyanamide and carbon
Nitrolim: 1. Chemical name of urea
Carbamide: 3. A mixture of ammonium carbonate and lime water

Question 3.

Column A     Column B
Nessler’s reagent 1. Used in making gas thermometers
Vanadium pentoxide 2. Alkaline solution of potassium mercuric iodide
Nitrogen 3. Catalytic oxidation of ammonia to produce NO
Ostwald’s process 4. Catalyst used in contact process of H2SO4 synthesis

 

Answer:
Nessler’s reagent:  2. Alkaline solution of potassium mercuric iodide
Vanadium pentoxide: 4. Catalyst used in contact process of H2SO4 synthesis
Nitrogen:  1. Used in making gas thermometers
Ostwald’s process: 3. Catalytic oxidation of ammonia to produce NO

WBBSE Solutions for Class 10 Physical Science and Environment

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