WBBSE Solutions For Class 10 Physical Science And Environment Physical And Chemical Properties Of Elements Metallurgy

Metallurgy Topic A Ores, Minerals And Alloys Synopsis:

1. Metals such as, iron, copper, zinc, aluminium etc., have immense practical applications in our daily life.
2. Naturally occurring inorganic substances derived from the earth’s crust which contain metals in their free state or in the form of compounds along with earthy and rocky impurities are called minerals.
3. Minerals from which high-grade metals can be conveniently and economically extracted on a large scale are called ores.
4. All ores are minerals, but all minerals are not ores.
5. A homogeneous or heterogeneous mixture of two or more metals or a metal and a nonmetal having different characteristic properties than the constituent elements is called an alloy.
6. Alloys are stronger, have greater tensile strength and are less reactive than the individual constituent metals or non-metals. These properties make them less susceptible towards corrosion and weathering.

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Metallurgy Topic A Ores, Minerals And Alloys Short And Long Answer Type Questions:

 

Question 1. Classify iron on the basis of carbon content. Which among these is the purest?

Answer:

Classification Of iron on the basis of carbon content

1. On the basis a carbon content, iron is divided into three categories—cast iron (C: 2-4.5%), wrought iron (C: 0.1-0.15%) and steel (C: 0.151.5%).
2. Wrought iron is the purest form of iron.

Question 2. Write some uses of cast iron.

Answer:

Cast iron is used in the making of

1. Wrought iron and steel
2. Tubes, iron, railing, cauldron, lamp post etc.

Question 3. Write some uses of wrought iron.

Answer:

Wrought iron is used in the making of

1. Core of electromagnet
2. Wires, nails, rods, chains etc.

Wbbse Class 10 Physical Science Solutions

Question 4. Write some uses of steel.

Answer:

Some uses of steel:

Steel finds extensive use in modern civilization. It is used in the making of
1. Automobiles, rails, knives, scissors, surgical instruments, ships, blades tankers etc.
2. Cooking utensils,
3. Alloy steel is made by adding other metals with steel.

Question 5. Why is copper used in the making of electrical wires and instruments?

Answer: Copper is a metal of low resistance and high malleability. Thus, it has a high value of electrical conductance and also it can be easily shaped into wires . Hence, it is used in the making of electrical wires and instruments.

Question 6. Copper is a good conductor – of heat— state one application of this property.

Answer:

Copper is a good conductor – of heat

1. Copper is used in making cooking utensils because it is a good conductor of heat.
2. Copper is used in the construction of a calorimeter which is quite helpful in measuring the amount of absorbed or released heat.
3. Copper is used in the making of boilers in factories. Being a good conductor it helps in boiling of water quickly.

Wbbse Class 10 Physical Science Solutions

Question 7. Write some important uses of zinc.

Answer:

Some important uses of zinc:

1. Zinc is used as a reagent in the laboratory for the preparation of hydrogen.
2. It is used in electrochemical cells and batteries.
3. It is also used in making of zinc white.
4. Zinc is coated over iron to protect it from rusting.

Question 8. Aluminium is a light non-corrosive metal—state application of this property.

Answer:

Aluminium is a light non-corrosive metal

1. Being a light metal aluminium is used in the manufacture of body parts of machines.
2. As it is non-corrosive and light, it is used in making the body of automobiles, aeroplanes, window frames, buckets, tanks, boxes etc.

Question 9. Some properties of aluminium are mentioned below. State the applications of these properties.
1. Aluminium is a good conductor of electricity.
2. Aluminium can be easily beaten into thin sheets.

Answer:
1. Aluminium is a good conductor of electricity. Hence, it is used for making electrical wires and electrical instruments.
2. Aluminium can be easily beaten into thin sheets. Due to this property, aluminium is used in making packing foils.

Wbbse Class 10 Physical Science Solutions

Question 10. What is an alloy? Name a common alloy and state its composition.

Answer:

Alloy:

1. An alloy is a homogeneous or heterogeneous mixture of two or more metals or sometimes of metals and non-metals having characteristic properties different from their constituent elements.
2. A common and widely used alloy is brass. It is made of copper (60-80%) and zinc (20-40%).

 

 

 

Question 11. State two important characteristics of alloys.

Answer:

Some important characteristics of alloys are discussed below—

1. An alloy may be homogeneous or heterogeneous in nature.
2. An alloy has different characteristic properties than its constituent metals.

Wbbse Class 10 Physical Science Solutions

Question 12. Write down the advantages of using alloys.

Answer:

The advantages of using alloys are—

1. Alloys have more tensile strength than their constituent elements. E.g., brass or bell metal is more tensile than copper.
2. Metals melt at very high temperatures. When a pure metal is alloyed with another metal or non-metal, its melting point generally reduces.
3. Metals are extremely susceptible to chemical and weather attacks. Alloys are more resistant to corrosion. When a metal is alloyed, it becomes less reactive, thereby enhancing its corrosion resistance.
4. To increase or decrease the conductivity of metals, alloying can be done. E.g., specific resistance of nichrome is greater than its component metals, i.e., conductivity of nichrome is less than that of its component metals and thus it is used in an electric heater.

Question 13. Name two alloys of iron, state their compositions and mention some uses of these alloys.

Answer:

Composition and uses of alloys of iron are:

Alloy	Composition	Uses
Stainless steel	Fe: 73%, Cr: 18%, Ni: 8%, C: 1%	In making of utensils, knife, scissors, surgical instruments, machine parts etc.
Nickel steel	Fe: 96-98%, Ni: 2-4%	Manufacturing automobile parts, gear, propellers of aircraft, cables etc.

Question 14. Give the composition And uses of two alloys containing both copper and zinc as their constituents.

Answer: Brass and bronze contain both copper and zinc as their constituents.

Wbbse Class 10 Physical Science Solutions

Alloy	Composition	Uses
Brass	Cu: 60-80%, Zn: 20-40%	Making parts of telescopes, barometer etc., utensils, pipes, statues etc.
Bronze	Cu: 80%, Sn: 18%, Zn: 2%	Making statues, coins, utensils, medals etc.

Question 15. Write down the name of the main component of brass. Why is the use of brass more advantageous than that of its main component?

Answer:

The main component of brass is copper (Cu: 6080%, Zn: 20-40%). The advantages of using brass compared to copper are as follows—

1. Brass has more tensile strength than soft metal copper.
2. Reactivity of brass is less than that of copper and hence brass is less corrosive in nature.

Question 16. Write down the name, composition and uses of some alloys of aluminium.
Answer:

The name, composition and uses of some alloys of aluminium are—

Alloy	Composition	Use
Magnelium	Al = 90-95%, Mg = 5-10%	Parts of aeroplanes, balance and scientific apparatus are made with magnelium.
Duralumin	Al = 95%, Cu = 4%, Mg = 0.5%, Mn = 0.5%	Parts of aeroplane and motor car, pressure cookers are made with duralumin.
Aluminium- bronze	Al = 10%, Cu = 90%	Coin, statues, flower vases, and cooking utensils are made with aluminium bronze.
Alnico	Fe = 60%, Ni = 20%, Al = 12%, Co = 8%	Permanent magnets of high power are made with alnico.

Question 17. What do you mean by amalgam and give example; Mention some uses of mercury alloys.

Answer:

Amalgam:

The alloys which contain mercury (Hg) as one of their constituents are commonly known as amalgams. E.g., sodium amalgam (Na-Hg), magnesium amalgam (Mg-Hg) etc.

The uses of mercury alloys, i.e., amalgams are as follows—
1. Tin-amalgam (Sn-Hg) is used in the preparation of the mirror.
2. Sodium-amalgam (Na-Hg) and zinc-amalgam (Zn-Hg) are used as reagents (reductants) in organic reactions.
3. Silver amalgam (Ag-Hg) is used in dental treatment.

Question 18. Define minerals and give examples.

Answer:

Minerals:

Minerals may be defined as the naturally occurring inorganic substances found in the earth’s crust or on earth surface which contains metals in their native state or in the form of compounds mixed with other impurities. For example—red haematite (Fe₂O₃), magnetite (Fe₂O₄), and iron pyrites (FeS₂) are minerals containing iron.

 

Question 19. Define ores and give examples.

Answer:

Ores:

The minerals from which a metal can be conveniently and economically extracted are known as ores of the metal. For example—High quality iron can be conveniently and economically extracted from red haematite (Fe₂O₃). Hence, red haematite is an ore of iron.

Similarly, malachite [CuCO₃ • Cu(OH)₂ ] is an ore of copper.

Question 20. Differentiate between monerals and ores.

Answer:

The major differences between minerals and ores are:

Minerals	Ores
Minerals    are inorganic substances found in the earth’s crust containing one or more metals, in their native state or as their compounds, along with impurities. For example, copper pyrites (Cu2S-Fe2S3) is a mineral of copper.	The minerals from which a metal can be conveniently and    economically extracted involving less complex-    chemical methods are called ores of that metal. For example, red haematite (Fe2O3) and iron pyrites (FeS2) both are minerals of iron but only iron pyrites is the ore of iron not haematite.
All minerals are not ores.	All ores are minerals.

Question 21. All ores are minerals, but all minerals are not ores – justify the statement.

Answer:

All ores are minerals, but all minerals are not ores

Minerals are the naturally occuring inorganic substances which contain one or more metals, in their native state or as their compounds, along with impurities.

On the other hand, the minerals from which a metal can be conveniently and economically extracted are called ores of that metal. Obviously, all ores are minerals.

But, we cannot extract metals from any mineral by convenient and cheap methods. Hence, all minerals cannot be called ores.

For example, both bauxite and china-clay are the minerals of aluminium. But, only bauxite is considered as the ore of aluminium, not china-clay.

Question 22. Why zinc belend can be termed as both mineral and ore?

Answer: Zinc blend (ZnS) is a solid metal compound which can be found in earth crust or in mines. Hence it can be termed as mineral of zinc. Moreover, high quality metallic zinc can be extracted from zinc blend using easier metallurgical technique. Hence zinc blend can be termed as ore of zinc metal, too.

Question 23. Write down the name and formula of important ores of copper.

Answer: Oxide ore — cuprite (Cu₂O)
Sulphide ore — copper pyrites (Cu₂S-  Fe₂S₃ or CuFeS₂), copper glance – (Cu₂S)
Carbonate ore — malachite [CuCO₃ • Cu(OH)₂]

Question 24. Write down the names of important ores of iron.

Answer: Oxide ore — red haematite (Fe₂O₃), magnetite (Fe₂O₄)
Carbonate ore — spathic iron orsedarite (Fe₂O₃)

Question 25. Write down the names of important ores of zinc.

Answer: Oxide ore — zincite (ZnO)
Sulphide ore — zinc blend (ZnS)
Carbonate ore — calamine (ZnCO₃)

Question 26. Write down the names of important ores of aluminium.

Answer: Oxide ore — bauxite ( Al₂O₃ • H₂O), gibbsite (Al₂O₃-3H₂O)
Fluoride ore — cryolite (AIF₃ • 2NaF)

Metallurgy Topic A Ores, Minerals And Alloys Very Short Answer Type Questions Choose The Correct Answer:

 

Question 1. The core of an electromagnet is made of
1. Cast iron
2. Steel
3. Wrought iron
4. Magnetite

Answer: 3. Wrought iron

Question 2. The metal used in making of electrolytic cells and dry cells is
1. Al
2. Sn
3. Zn
4. Cu

Answer: 3. Zn

Question 3. Which of the following is the purest form of iron?
1. Cast iron
2. Wrought iron
3. Steel
4. Invar

Answer: 2. Wrought iron

Question 4. The amount of carbon present in steel is
1. 0.01-0.2%
2. 0.15-1.5%
3. 2-4.5%
4. 5-5.6%

Answer: 2. 0.15-1.5%

Question 5. Which of the following is not a constituent of the alloy, duralumin?
1. Copper
2. Magnesium
3. Manganese
4. Nickel

Answer: 4. Nickel

Question 6. The percentage of silver in German silver is
1. 2-5%
2. 5-10%
3. 10-15%
4. 0%

Answer: 4. 0%

Question 7. Which of the following alloys does not contain zinc as a constituent metal?
1. Brass
2. German silver
3. Bell metal
4. Gem metal

Answer: 3. Bell metal

Question 8. Which of the following alloys does not contain nickel as a constituent metal?
1. Stainless steel
2. Manganese steel
3. German silver
4. Invar

Answer: 2. Manganese steel

Question 9. Which of the following minerals is not an ore?
1. Red haematite
2. Zinc blende
3. Bauxite
4. Iron pyrites

Answer: 4. Iron pyrites

Question 10. The oxide ore of zinc is
1. Calamine
2. Zinc blende
3. Zincite
4. Willemite

Answer: 3. Zincite

Question 11. Tin-amalgam is used
1. To make spectacles
2. As a reducing agent
3. To make mirrors
4. To make thermometers

Answer: 3. To make mirrors

Question 12. Which of the following is a mineral of iron but not its ore?
1. Red haematite
2. Magnetite
3. iron pyrites
4. Siderite

Answer: 3. iron pyrites

Question 13. Gibbsite is the ore of
1. Al
2. Cu
3. Zn
4. Fe

Answer: 1. Al

Question 14. Calamine is the ore of
1. Iron
2. Copper
3. zinc
4. Aluminium

Answer: 3. zinc

Question 15. Components of German silver are
1. Cu, Zn, Sn
2. Al, Cu, Mg, Mn
3. Fe, Cr, Ni, C
4. Cu, Zn, Ni

Answer: 4. Cu, Zn, Ni

Question 16. Which one of the following is the ore of aluminium?
1. Red haematite
2. Malachite
3. Chalcopyrites
4. Bauxite

Answer: 4. Bauxite

Question 17. Main component of duralumin is
1. Al
2. Mg
3. Cu
4. Sn

Answer: 1. Al

Question 18. Chalcopyrites is the ore of
1. Zn
2. Fe
3. Mg
4. Cu

Answer: 4. Cu

Question 19. Which of the following is a sulphide ore?
1. Bauxite
2. Zincite
3. Haematite
4. Zinc blende

Answer: 4. Zinc blende

Question 20. Composition of brass is
1. Cu and Sn
2. Zn and Cu
3. Cu and Pb
4. Cu and Al

Answer: 2. Zn and Cu

Question 21. Which of the following is not an ore of Cu?
1. Haematite
2. Chalcocite
3. Azurite
4. Malachite

Answer: 1. Haematite

Question 22. Which of the following metal pair is present in both bronze and bell metal?
1. Iron, nickel
2. Copper, tin
3. Zinc, copper
4. Iron, tin

Answer: 2. Copper, tin

Question 23. Among the components of amalgam, one must be
1. Fe
2. Ag
3. Au
4. Hg

Answer: 4. Hg

Question 24. The amount of carbon is highest in
1. Steel
2. Wrought iron
3. Cast iron
4. Chrome steel

Answer: 3. Cast iron

Question 25. The alloy used in preparation of the structure of aeroplane is
1. German silver
2. Bronze
3. Invar
4. Duralumin

Answer: 4. Duralumin

Question 26. Haematite is the ore of
1. Copper
2. Aluminium
3. Iron
4. Zinc

Answer: 3. Iron

Question 27. Which one of the following metal is present in china clay?
1. Cu
2. Al
3. Fe
4. Zn

Answer: 2. Al

Question 28. Which one of the following contains aluminium?
1. Bronze
2. Bell metal
3. German silver
4. Duralumin

Answer: 4. Duralumin

Question 29. Percentage of carbon in wrought iron is
1. 0.1-0.15%
2. 0.16-0.6%
3. 2-2.5%
4. 3-3.5%

Answer: 1. 0.1-0.15%

Question 30. The main component of magnelium is
1. Mn
2. Al
3. Mg
4. C

Answer: 2. Al

Question 31. Which one of the following alloys contains zinc?
1. Bell metal
2. Brass
3. Bronze
4. Duralumin

Answer: 2. Brass

Question 32. Which of the following is the formula of bauxite?
1. Al₂O₃  
2. Al₂O₃ .H₂O
3. Al₂O₃ .2H₂O
4. AlF₃.3NaF

Answer:

Metallurgy Topic A Ores, Minerals And Alloys Answer In Brief:

Question 1. Arrange wrought iron, steel and cast iron in the order of increasing carbon content present in them.
Answer: Wrought iron < steel < cast iron.

Question 2. Which metal is present in each of bronze, brass and bell metal?
Answer: In each of bronze, brass and bell metal, copper is present.

Question 3. What are the major constituents of stainless steel?
Answer: The major constituents of stainless steel are iron (73%), chromium (18%) and nickel (8%).

Question 4. Name any two alloys of aluminium.
Answer: Two alloys of aluminium are—
1. Magnelium (Mg, Al) and
2. Alnico (Al, Ni, Co, Fe).

Question 5. Name any two alloys of iron.
Answer: Two alloys of iron are—
1. Stainless steel (Fe, Cr, Ni and traces of carbon) and
2. Invar(Fe, NO.)

Question 6. Name any two alloys of zinc.
Answer: Two alloys of zinc are 0 brass (Cu, Zn) and 0 german silver (Cu, Zn, Ni).

Question 7. Name some important ores of iron.
Answer: Some important ores of iron are red haematite (Fe₂O₃), magnetite (Fe₂O₄), siderite (Fe₂O₃) etc.

Question 8. Name some important ores of copper with their formulas.
Answer: Some important ores of copper are copper pyrites [(Cu₂S • Fe₂S₃) or CuFeS₂], copper glance (Cu₂S), malachite [CuCO₃ • Cu(OH)₂] , cuprite (Cu₂O) etc.

Question 9. Name the major ores of zinc with their respective formulas.
Answer: The major ores of zinc are zinc blende (ZnS), calamine (ZnCO₃), zincite (ZnO) etc.

Question 10. Name the major ores of aluminium with their respective formulas.
Answer: The major ores of aluminium are bauxite. (Al₂O₃-2H₂O), gibbsite (Al₂O₃ • 3H₂O), cryolite (AlF₃• 3NaF) etc.

Question 11. Name a mineral of aluminium which is not considered as its ore.
Answer: China-clay ( Al₂O₃ • 2SiO₂• 2H₂O) is a mineral of aluminium but is not considered as its ore.

Question 12. Name a metal which is found in nature in its free state.
Answer: Gold (Au) is found in nature in its free state.

Question 13. Why is invar used in making metre scale?
Answer: Invar is used in making metre scale because its coefficient of linear expansion is very small.

Question 14. What are noble metals? Give examples.
Answer: The metals which are chemically not so reactive are known as noble metals. Example: Gold, platinum.

Question 15. Write down the percentage of carbon in wrought iron.
Answer: The percentage of carbon in wrought iron is 0.1-0.15%.

Question 16. Which type of iron is used to prepare electric iron?
Answer: Cast iron is used to prepare electric iron.

Question 17. Which metallic powder is mixed with ammonium nitrate to prepare the explosive called ‘ammonal’?
Answer: Aluminium powder.

Question 18. Why is copper used as an electrode in electrical cells?
Answer: Due to its high electrical conductivity.

Question 19. Which metal is used to prepare calorimeter and why?
Answer: Copper, due to its high conductivity of heat, is used to prepare calorimeter.

Question 20. Which metal is used in print-block?
Answer: Zinc is used to prepare print blocks.

Question 21. Mention the metallic components of bronze?
Answer: Copper (80%), tin (18%) and zinc (2%).

Question 22. Name the metal pair which is present in both of bronze and bell metal.
Answer: Copper and tin.

Question 23. Which metal is common in brass and bronze?
Answer: Copper.

Question 24. Name the non-transition metal present in bell-metal.
Answer: Tin (Sn).

Question 25. Percentage of which metal is higher in brass?
Answer: Copper (60-80%).

Question 26. Write down the composition of German silver.
Answer: Cu: 50%, Zn: 20%, Ni: 30%

Question 27. Write down the name of the main component of duralumin.
Answer: Aluminium (95%).

Question 28. Which alloy is used to prepare the structure of aeroplane?
Answer: Duralumin is used to prepare the structure of aeroplane

Question 29. Give examples of two alloys made up of four metals.
Answer: Duralumin (Al + Cu + Mn + Mg) and alnico (Fe + Ni + Al + Co).

Question 30. Which alloy is used to prepare permanent magnet?
Answer: Alnico (Fe + Ni + Al + Co).

Question 31. Which alloy is used to prepare pressure cooker?
Answer: Duralumin.

Question 32. Which one of iron pyrites and red haematite, is the ore of iron?
Answer: Red haematite is the ore of iron.

Question 33.Write down the name and formula of a substance which is a mineral of iron but not its ore.
Answer: Iron pyrites (FeS₂).

Question 34. Calamine is the ore of which metal?
Answer: Calamine (ZnCO₃) is the ore of zinc.

Question 35. Write down the formula of zinc white?
Answer: Chemical formula of zinc white is ZnO.

Question 36. Write down the formula of the ore— Gibbsite.
Answer: The formula of Gibbsite is Al₂O₃ • 3H₂O.

Metallurgy Topic A Ores, Minerals And Alloys Fill In The Blanks:

Question 1. An explosive is prepared by mixing _______ powder with ammonium nitrate.
Answer: Aluminium

Question 2. The percentage of carbon in wrought iron is ______ %.
Answer: 0.1-0.15

Question 3. The non-metal present in stainless steel is _______
Answer: Carbon

Question 4. The carbonate ore of iron is ________
Answer: Siderite

Question 5. The amalgam of _______ metal is used as a reducing agent in organic reactions.
Answer: Sodium

Question 6. The alloy of aluminium used in making electromagnets is _______
Answer: Alnico

Question 7. Metals can be extracted conveniently and economically from their ______
Answer: Ores

Question 8. Cryolite is an ore of _______
Answer: Aluminium

Question 9. The oxide ore of copper is ______
Answer: cuprite

Question 10. ________ foil is used for packaging of food.
Answer: Aluminium

Question 11. German silver is the alloy of ____ and nickel.
Answer: Copper(Cu₂O)

Question 12. Percentage of silver in German silver is _______
Answer: Zero

Question 13. The main component of duralumin is ______
Answer: Aluminium

Question 14. If one of the components of an alloy be mercury, then the alloy is termed as an ________
Answer: Amalgam

Question 15. ________ is the ore of aluminium.
Answer: Gibbiste/Bauxite

Question 16. All the ores are minerals, but all of the minerals are not _____
Answer: Ores

Question 17. Name of the sulphide ore of copper is ______
Answer: Copper glance

Question 18. Formula of baixite is _______
Answer: Al₂O₃ 

Metallurgy Topic A Ores, Minerals And Alloys State Whether True Or False:

Question 1. All minerals are ores, but all ores are not minerals.
Answer: False

Question 2. Calamine is the chief ore of zinc.
Answer: True

Question 3. Cast iron is the purest form of iron.
Answer: False

Question 4. Zincite is the oxide ore of zinc.
Answer: True

Question 5. The percentage of silver present in the alloy German silver is 2-5%.
Answer: False

Question 6. Tin-amalgam is used to make spectacles.
Answer: False

Question 7. The alloy named invar is used to prepare metre-scale.
Answer: True

Question 8. A component of bell-metal is zinc.
Answer: False

Question 9. Components of brass are Cu and Sn. Chalcosite is the ore of copper.
Answer: False

Question 10. Chalcosite is the ore of copper.
Answer: True

Metallurgy Topic B Principles Of Metal Extraction And Oxidation-Reduction Synopsis:

 

1. A chemical reaction in which an atom, an ion or a molecule loses one or more electrons is called an oxidation reaction.
2. A chemical reaction in which an atom, an ion or a molecule gains one or more electrons is called a reduction reaction.
3. Extraction of a metal from its corresponding oxide by elimination of oxygen is known as reduction.
4. Extraction of metals such as iron, chromium, manganese etc., from their oxides by heating the oxides with aluminium powder at a high temperature is known as Goldschmidt’s thermite process.
5. A mixture of 3 parts of Al₂O₃ and 1 part of aluminium powder is known as thermite mixture.
6. The vertical arrangement of metals in decreasing order of their relative reactivity is known as metal activity series.
7. A metal occupying a higher position (more reactive) in the metal activity series can displace another metal occupying a relatively lower position(less reactive) from the aqueous solution of its salt.
8. Metals present in the middle of the activity series such as Zn, Fe etc., can be extracted from their ores by carbon reduction process.
9. Metals present at the top of the metal activity series are extracted by electrolysis of their fused salts.

Metallurgy Topic B Principles Of Metal Extraction And Oxidation-Reduction Short And Long Answer Type Questions:

 

Question 1. How does oxidation occur?

Answer: Oxidation takes place in three different ways—
1. Oxidation takes place when an atom loses electron(s).
Example—\(\mathrm{Na}+\rightarrow \mathrm{Na}^{+}+e ; \mathrm{Al} \rightarrow \mathrm{Al}^{3+}+3 e\)

2. Oxidation takes place when a cation loses electron(s).
Example— \(\begin{aligned}
& \mathrm{Cu}^{+} \rightarrow \mathrm{Cu}^{2+}+e \\
& \mathrm{Fe}^{2+} \rightarrow \mathrm{Fe}^{3+}+e
\end{aligned}\)

3. Oxidation takes place when an anion loses an electron(s).
Example— \(\mathrm{S}^{2-} \rightarrow \mathrm{S}+2 e ; 2 \mathrm{Cl}^{-} \rightarrow \mathrm{Cl}_2+2 e\)

Question 2. How does reduction occur?

Answer: Reduction takes place in four different ways—
1. Reduction takes place when an atom accepts electron(s).
Example: \(\mathrm{Cl}+e \rightarrow \mathrm{Cl}^{-} ; \mathrm{O}+2 e \rightarrow \mathrm{O}^{2-}\)

2. Reduction takes place when a cation accepts electron(s).

Example: \(\mathrm{Na}^{+}+e \rightarrow \mathrm{Na} ; \mathrm{Mg}^{2+}+2 e \rightarrow \mathrm{Mg}\)

3. Reduction takes place when an anion of lower charge accepts electron(s) and is converted into an anion of higher charge.

Example: \(\begin{aligned}
& \mathrm{MnO}_4^{-}+e \rightarrow \mathrm{MnO}_4^{2-} \\
& \mathrm{O}^{-}+e \rightarrow \mathrm{O}^{2-}
\end{aligned}\)

4. Reduction takes place when a cation of higher charge accepts electron and is converted into another cation of lower charge.

Example: \(\begin{aligned}
& \mathrm{Fe}^{3+}+e \rightarrow \mathrm{Fe}^{2+} ; \\
& \mathrm{Sn}^{4+}+2 e \rightarrow \mathrm{Sn}^{2+}
\end{aligned}\)

Question 3. Discuss the electronic theory of oxidation and reduction.

Answer:

The electronic theory of oxidation and reduction

Oxidation: The process of removal of one or more electrons from an atom or ion is known as oxidation.

Example: \(\mathrm{Na} \rightarrow \mathrm{Na}^{+}+e, \mathrm{Fe}^{2+} \rightarrow \mathrm{Fe}^{3+}+e\)

Reduction: The process of acceptance of one or more electrons by an atom or ion is known as reduction.

Example: \(\mathrm{Cl}+e \rightarrow \mathrm{Cl}^{-}, \mathrm{Na}^{+}+e \rightarrow \mathrm{Na}\)

Question 4. Identify which one is oxidation and which one is reduction— \(\mathrm{Ca} \rightarrow \mathrm{Ca}^{2+}+2 e ; \mathrm{O}+2 e \rightarrow \mathrm{O}^{2-}\)

Answer: \(\mathrm{Ca} \rightarrow \mathrm{Ca}^{2+}+2 e\) – In this reaction a Ca-atom loses two electrons to form Ca²⁺ ion. Hence it is an oxidation reaction as loss of electrons means oxidation.

\(\mathrm{O}+2 e \rightarrow \mathrm{O}^{2-}\) —In this reaction an O-atom gains two electrons to form O^2- ion. Since gaining of electrons is termed as reduction, so this reaction is a reduction process.

Question 5. With the help of electronic theory, show that oxidation and reduction occur simultaneously in the following reaction: \(2 \mathrm{Fe}^{3+}+\mathrm{Sn}^{2+} \rightarrow 2 \mathrm{Fe}^{2+}+\mathrm{Sn}^{4+}\)

Answer: \(2 \mathrm{Fe}^{3+}+\mathrm{Sn}^{2+} \rightarrow 2 \mathrm{Fe}^{2+}+\mathrm{Sn}^{4+}\)

 

Here each Fe³⁺ ion accepts an electron to form Fe²⁺ ion. Hence it is a reduction process as gaining of electron is termed as reduction.

\(\mathrm{Fe}^{3+}+e \rightarrow \mathrm{Fe}^{2+}\)

 

Again each Sn²⁺ ion loses 2 electrons from its valence shell. Hence the process is oxidation as losing of electron in termed as oxidation.

\(\mathrm{Sn}^{2+} \rightarrow \mathrm{Sn}^{4+}+2 e\)

 

Hence, it can be said that oxidation and reduction occur simultaneously.

Question 6. Extraction of metals from their ores is basically a reduction process—explain with example.

Answer:

Extraction of metals from their ores is basically a reduction process

In the ore, metal remains in a positive oxidation state but, after extraction of the metal, the oxidation number becomes zero. Thus, during extraction of the metal, the metal ion accepts electron to become a free atom. Hence, we can say that extraction of metals from its ores is a reduction process.

\(\mathrm{M}^{n+}(\text { metal ion })+\text { ne } \rightarrow \mathrm{M}(\text { free metal })\)

 

Example: Zinc oxide (ZnO) is mixed with excess coke and heated at a temperature of about 1300-1400°C in a retort when zinc oxide is reduced to metallic zinc.

\(\mathrm{ZnO}+\mathrm{C} \rightarrow \mathrm{Zn}+\mathrm{CO} \uparrow\)

 

Question 7. What do you mean by metal activity series? Name the metals at the top and bottom of the series.

Answer:

Metal activity series:

1. The series obtained by vertically arranging the metals from top to bottom in decreasing order of their electropositivity or decreasing order of chemical reactivity is called metal activity series.
2. The metal placed at the top of the series is potassium (K) while gold (Au) is placed at the bottom.

Question 8. Arrange Cu, Fe, Ag and Zn in increasing order of their reactivity on the basis of the following reactions.
1. CuSO₄+ Fe → FeSO₄ + Cu
2. 2AgNO₃ + Cu → Cu(NO₃)₂+ 2Ag
3. FeSO₄ + Zn → ZnSO₄+ Fe

Answer: A more reactive metal replaces a less reactive metal from its salt. So, according to reaction,
1. Fe is more reactive than Cu. According to reaction,
2. Cu is more reactive than Ag. According to reaction,
3. Zn is more reactive than Fe

Hence, the order of increasing reactivity: \(\mathrm{Ag}<\mathrm{Cu}<\mathrm{Fe}<\mathrm{Zn}\)

Question 9. How are the metals placed at the top of the metal activity series extracted?

Answer: These metals are usually extracted by electrolytic method. The molten hydroxide or chloride salts of the metal is electrolysed using suitable electrodes, and the metal deposits on the cathode.

For example, sodium is extracted by electrolysing a molten solution of sodium chloride using iron cathode and graphite anode. Sodium is deposited at the cathode.

Dissociation of NaCI: \(\mathrm{NaCl} \text { (molten) } \rightarrow \mathrm{Na}^{+}+\mathrm{Cl}^{-}\)

Reaction at cathode: \(\mathrm{Na}^{+}+e \rightarrow \mathrm{Na}\)

Reaction at anode: \(\begin{aligned}
& \mathrm{Cl}^{-} \rightarrow \mathrm{Cl}+e \text { (oxidation); } \\
& \mathrm{Cl}+\mathrm{Cl} \rightarrow \mathrm{Cl}_2 \text { (reduction) }
\end{aligned}\)

Question 10. Describe the extraction of aluminium from pure alumina by electrolytic method.

Answer:

The extraction of aluminium from pure alumina by electrolytic method

Aluminium is generally extracted from bauxite ore  Al₂O₃ -2H₂O. At first, bauxite is converted into pure alumina. Pure alumina is then mixed with proportionate amount of cryolite (CaF₂) and fluorspar (AIF₃ • 3NaF) and the mixture is heated at around 900°C. When electricity is passed through the fused mixture, aluminium is deposited at the cathode.

Electrolytic dissociation: \(\left.\mathrm{Al}_2 \mathrm{O}_3 \text { (molten }\right) \rightarrow 2 \mathrm{Al}^{3+}+3 \mathrm{O}^{2-}\)

Cathode reaction: \(2 \mathrm{Al}^{3+}+6 e \rightarrow 2 \mathrm{Al}\)

Anode reaction: \(\begin{aligned}
& 3 \mathrm{O}^{2-} \rightarrow 3 \mathrm{O}+6 e \\
& 3 \mathrm{O}+3 \mathrm{O} \rightarrow 3 \mathrm{O}_2
\end{aligned}\)

Question 11. Why are the strong electropositive metals like Na, K etc., not extracted from the aqueous solution of their salts?

Answer: An aqueous solution of a salt of a strong electropositive metal contains H⁺ ions formed due to dissociation of water, along with the metal cations. Now, the tendency of H+ ions to be discharged at cathode is stronger than that of metals like Na, K etc.

Hence, on electrolysis of the aqueous solution, H+ ions will be reduced at cathode instead of metal ions. Hence, hydrogen gas will be produced at cathode instead of desired metal. This is why a strong electropositive metal is extracted from its salt by electrolysis of the fused salt but not the aqueous solution of the salt.

Question 12. Which method is suitably used for the extraction of metals (such as Fe, Zn etc.) occupying the middle part of the metal activity series? Explain with reasons.

Answer: The metals occupying the middle part of the metal activity series are moderately reactive and hence have relatively less tendency than carbon to combine with oxygen. Therefore, these metals can be extracted from their oxides by carbon reduction process at high temperature.

Example: \(\mathrm{ZnO}+\mathrm{C}(\text { coke }) \rightarrow \mathrm{Zn}+\mathrm{CO}\)

Question 13. When an iron nail is dipped into an aqueous solution of copper sulphate, a reddish-brown layer is developed over the nail. Explain why.

Answer: A metal occupying a higher position relative to another metal in the metal activity series can replace the latter from the solution of it’s salt. In metal activity series, iron is placed above copper.

Hence iron can replace copper from copper sulphate solution. So, when an iron nail is dipped into an aqueous copper sulphate solution, reaction takes place between them at the surface of iron nail and hence a reddish brown layer of metallic copper is formed over the iron nail.

\(\mathrm{Fe}+\mathrm{CuSO}_4 \rightarrow \mathrm{FeSO}_4+\mathrm{Cu} \downarrow \text { (red) }\)

 

 

Question 14. What happens when a piece of zinc is added to an aqueous solution of copper sulphate?

Answer: In the metal activity series, zinc is placed above copper. Hence zinc can replace copper from copper sulphate solution. So, when a small piece of zinc is dipped in copper sulphate solution, reaction takes place between zinc and copper sulphate and copper is precipitated. The precipitated copper deposits on the surface of zinc and hence a reddish brown layer is formed over zinc.

\(\mathrm{Zn}+\mathrm{CuSO}_4 \rightarrow \mathrm{ZnSO}_4+\mathrm{Cu} \downarrow \text { (red) }\)

 

Question 15. What is carbon reduction process metal extraction?

Answer: Reduction of a metal oxide by heating the mixture of metal oxide with carbon at a very high temperature in a blast furnace is called carbon reduction process. ‘Coke powder’ is used as a reducing agent for this process. Besides, CO produced due to incomplete oxidation of carbon also acts as reducing agent.

Question 16. Aluminium cannot be extracted by carbon reduction process. Explain with reasons.

Answer:

Aluminium cannot be extracted by carbon reduction process.

Aluminium occupies the top portion of the metal activity series. Hence, it is a highly reactive metal and possesses strong reducing property. Carbon reduction process is applicable for the extraction of those metals which have relatively greater tendency to combine with carbon than oxygen.

However, aluminium has a greater tendency to combine with oxygen than carbon and also the oxide of aluminium (Al₂O₃) is more stable as compared to the oxides of carbon. Thus aluminium cannot be extracted by carbon reduction process. Al is generally extracted by electrolysis of molten alumina (Al₂O₃).

Question 17. How is zinc extracted by carbon reduction process?

Answer: During zinc extraction by carbon reduction process, the zinc ore, i.e., zinc blende (ZnS) or calamine (ZnCO₃) is converted into zinc oxide. Zinc oxide is then mixed well with excess coke powder.

The mixture is then taken in a retort made of fireclay and heated at a temperature of about 1300-1400°C. At this temperature zinc oxide is reduced to metallic zinc and carbon monoxide (CO) is evolved.

\(\mathrm{ZnO}+\mathrm{C} \rightarrow \mathrm{Zn}+\mathrm{CO} \uparrow\)

 

Coke acts as a reducing agent in this reaction.

Question 18. Write down advantages and disadvantages of carbon reduction process.

Answer:

Advantages of carbon reduction process:

1. The reductant used in this process, i.e., coke, is easily available and cheap.
2. Large amount of metal oxide can be reduced using a comparatively smaller amount of coke.
3. CO gas, formed in the reaction acts as reducing agent in addition to coke, in this process.

Disadvantages of carbon reduction process:

1. Highly electropositive metals like Na, K, Al, Mg etc., cannot be extracted by this process.
2. A few metals like Ca, Al etc., react with coke at higher temperature to form carbide compounds.

Question 19. Describe the principle of thermite process with example.

Answer:

The principle of thermite process with example:

Al has strong affinity for oxygen at high temperature. When oxides of relatively less reactive metals such as Fe, Mn, Cr etc., are heated with Al powder at a very high temperature, the oxides are reduced by Al to the corresponding metal.

This is the basic principle of Goldsmith’s thermite process. The process produces large amount of heat and the reaction temperature reaches as high as 2000°C. At this temperature, the extracted metal is obtained in molten state.

 

Question 20. What is thermite mixture? Write two practical applications of thermite process.

Answer:

Thermite mixture

A mixture of 3 parts of ferric oxide (Fe₂O₃) by mass with 1 part of powdered aluminium is known as thermite mixture.

Some important applications of thermite process are discussed below—

1. Thermite process is applied in repairing broken parts of rails, tram lines, ship, machines made of iron etc.
2. Metals like chromium, manganese etc., are extracted by thermite process.

Question 21. What is used as reducing agent in thermite process? What is ignition mixture?

Answer:

1. Aluminium powder is used as reducing agent is thermite process.
2. In thermite process, thermite mixture is taken in a crucible made of fire clay (high temperature resistant). A mixture of magnesium powder and barium peroxide or potassium chlorate is taken over the thermite mixture which is then ignited with a burning magnesium ribbon. The mixture of magnesium powder and potassium chlorate or barium peroxide is called ignition mixture.

Question 22. State three advantages of thermite process.

Answer:

Three advantages of thermite process:

1. Metal extraction by thermite process doesn’t require large machineries. Metals can be extracted in small scale by this method for different purposes.

2. Broken parts of large machineries, rail lines, tram lines, ships can be repaired by thermite process. But, it .is not required to transport the damaged parts to the factories.

3. A huge quantity of Al₂O₃ is produced as a byproduct. This can be used for the preparation of emery powder used in metal polishing and manufacture of bricks used in the inner layer of furnace.

Question 23. Why are the metals occupying lower positions in the metal activity series often found in nature in their native state?

Answer: The metals occupying lower position in the metal activity series (Hg, Ag, Au) have very little chemical reactivity. Hence, they are not easily affected by atmospheric oxygen, water vapour, CO₂ etc., and thus exist in nature in their native state.

Question 24.
1. What happens when Al reacts with cone. NaOH solution?
2. What happens when steam is passed over red hot iron?Write down with equation.

Answer:
1. When Al reacts with cone. NaOH solution, sodium aluminate and hydrogen gas are formed.

\(2 \mathrm{Al}+2 \mathrm{NaOH}+2 \mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{NaAlO}_2+3 \mathrm{H}_2 \uparrow\)

 

2. When steam is passed over red hot iron, ferrosoferric oxide and hydrogen gas are formed.

\(3 \mathrm{Fe}+4 \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Fe}_3 \mathrm{O}_4+4 \mathrm{H}_2 \uparrow\)

 

Question 25. Write down the reaction occurs at cathode when an aqueous solution of MSO₄ (M = Metal) is electrolysed. State with reason whether the reaction is oxidation or reduction.

Answer: M²⁺ and H⁺ ions are present as cations in aqueous solution of MSO₄ due to following ionic dissocation:

\(\begin{aligned}
\mathrm{MSO}_4 & \rightleftharpoons \mathrm{M}^{2+}+\mathrm{SO}_4^{2-} \\
\mathrm{H}_2 \mathrm{O} & \rightleftharpoons \mathrm{H}^{+}+\mathrm{OH}^{-}
\end{aligned}\)

 

Therefore, the probable reactions at cathode:

\(\mathrm{M}^{2+}+2 e \rightarrow \mathrm{M} ; \mathrm{H}^{+}+e \rightarrow \mathrm{H} ; \mathrm{H}+\mathrm{H} \rightarrow \mathrm{H}_2 \uparrow\)

 

M²⁺ or H⁺ ion accepts electron to become electrically neutral at cathode. Hence reduction reaction takes pace at cathode.

Metallurgy Topic B Principles Of Metal Extraction And Oxidation-Reduction Very Short Answer Type Choose The Correct Answer:

Question 1. During extraction of aluminium, alumina is reduced by
1. H₂
2. Carbon
3. H₂S
4. Electrolysis

Answer: 4. Electrolysis

Question 2. During extraction of zinc, ZnO is reduced by
1. H₂
2. Carbon powder
3. H₂S
4. Electrolysis

Answer: 2. Carbon powder

Question 3. In thermite mixture, the ratio of Fe203 and Al powder is
1. 1:2
2. 2:1
3. 1:3
4. 3:1

Answer: 4. 3:1

Question 4. In thermite process, the substances present apart from the thermite mixture are
1. Fe, Cr
2. ZnO, Mg
3. BaO₂, Mn
4. BaO₂, Mg

Answer: 4. BaO₂, Mg

Question 5. Which of the following metals react with boiling water to evolve H₂ but does not do so with cold water?
1. Ca
2. K
3. Al
4. Na

Answer: 3. Al

Question 6. Which of the following metals is placed below Pb and above Hg in the metal activity series?
1. Sn
2. Ag
3. Cu
4. Au

Answer: 3. Cu

Question 7. Which of the following reactions is feasible?
1. \(\mathrm{Zn}+\mathrm{FeSO}_4 \rightarrow\)
2. \(\mathrm{MgSO}_4+\mathrm{Fe} \rightarrow\)
3. \(\mathrm{CuSO}_4+\mathrm{Ag} \rightarrow\)
4. \(\mathrm{ZnSO}_4+\mathrm{Pb} \rightarrow\)

Answer: 1. \(\mathrm{Zn}+\mathrm{FeSO}_4 \rightarrow\)

Question 8. Which of the following metals can be extracted by thermite process?
1. Fe
2. Cu
3. Zn
4. Al

Answer: 1. Fe

Question 9. In thermite process, the metal used as the reducing agent is
1. Al
2. Ni
3. Zn
4. Fe

Answer: 1. Al

Question 10. Metals placed at the top of the metal activity series are usually extracted by
1. Carbon reduction method
2. Reduction by H₂
3. Self-reduction
4. Electrolytic reduction

Answer: 4. Electrolytic reduction

Question 11. Metals placed at the middle region of the metal activity series are usually extracted by
1. Carbon reduction method
2. Reduction by H₂
3. Self-reduction
4. Electrolytic reduction

Answer: 1. Carbon reduction method

Question 12. Metals which can exist in free state in nature are
1. Placed at the top of the metal activity series
2. Placed at the middle of the metal activity series
3. Placed at the bottom of the metal activity series
4. Not included in the metal activity series

Answer: 3. Placed at the bottom of the metal activity series

Question 13. Which of the following orders correctly represents the reactivity of metals?
1. Pb < Fe < Mg
2. Mg > Ca > Zn
3. Ag < Zn < Pb
4. Al > Cu > Fe

Answer: 1. Pb < Fe < Mg

Question 14. Which of the following metal pairs reacts with both acids and alkalies to produce hydrogen gas?
1. Cu, Zn
2. Na, Cu
3. Pb, Zn
4. Al, Zn

Answer: 4. Al, Zn

Question 15. Na cannot be extracted from its oxide by carbon reduction process because
1. Oxide of Na is unstable
2. Na does not exist in its oxide form
3. Oxide of Na is more stable
4. Oxide of Na is volatile

Wbbse Class 10 Metallurgy Of Iron

Answer: 3. Oxide of Na is more stable

Question 16. Metals placed at the top of the metal activity series are
1. Strong reducing agents
2. Weak reducing agents
3. Strong oxidising agents
4. Weak oxidising agents

Answer: 1. Strong reducing agents

Question 17. In the metal activity series, the only non-metal present along with the metals is
1. Carbon
2. Hydrogen
3. Chlorine
4. Iodine

Answer: 2. Hydrogen

Question 18. Up Thermite mixture is
1. Fe₂O₃+ Al
2. Fe₂O₃ + Cu
3. FeO + Al
4. FeO + Cu

Answer: 1. Fe₂O₃+ Al

Question 19. In which of the following change incolouration can be observed when an iron nail is immersed in it
1. ZnSO₄
2. Al(SO₄)
3. FeSO₄
4. CuSO₄

Answer: 4. CuSO₄

Question 20. Which of the following metals does not react with boiling water, but forms H₂ in reaction with steam?
1. Mg
2. Zn
3. Fe
4. Al

Answer: 3. Fe

Question 21. Which of the following metals forms H2 when boiled with strong alkali?
1. Fe
2. Al
3. Cu
4. Mg

Answer: 2. Al

Wbbse Class 10 Metallurgy Of Iron

Question 22.Which of the following is used as reductant in the carbon reduction process of iron extraction?
1. Al
2. CO
3. CO₂
4. CO₃^2-

Answer: 2. CO

Question 23. In which of the following containers ferrous sulphate solution cannot be kept?
1. Copper container
2. Aluminium container
3. Silver container
4. None of the above

Answer: 2. Aluminium container

Question 24. The most reactive metal is
1. Fe
2. Ag
3. K
4. Cu

Answer: 3. K

Question 25. Which of the following metals reacts with water at normal temperature?
1. Na
2. Cu
3. Fe
4. Zn

Answer: 1. Na

Question 26. Which of the following metals cannot be extracted by electrolytic method?
1. Na
2. Zn
3. Al
4. Ca

Answer: 2. Zn

Question 27. Which of’the following can be extracted by carbon reduction method?
1. Al
2. Mg
3. Zn
4. Mn

Answer: 3. Zn

Question 28. The process of metal extraction by another metal is
1. Self-reduction
2. Electrolytic reduction
3. Thermite process
4. All of the above

Answer: 3. Thermite process

Wbbse Class 10 Metallurgy Of Iron

Question 29. The process of extraction of metal from ore is
1. Oxidation
2. Reduction
3. Redox
4. None of the above

Answer: 2. Reduction

Question 30. The oxidising agent in the thermite process is
1. Al
2. Mg-tape
3. Fe₂O₃
4. KClO₃

Answer: 3. Fe₂O₃

Metallurgy Topic B Principles Of Metal Extraction And Oxidation-Reduction Answer In Brief:

Question 1. Give an example of a reduction process where an anion accepts an electron.
Answer: \(\mathrm{MnO}_4^{-}+e \rightarrow \mathrm{MnO}_4^{2-}\)

Wbbse Class 10 Metallurgy Of Iron

In this reaction an anion accepts an electron and gets reduced.

Question 2. \(\mathrm{Cu}^{2+}+\mathrm{Zn} \rightarrow \mathrm{Cu}+\mathrm{Zn}^{2+}\)—

Identify the oxidant and reductant in the given reaction.

Answer: In the given reaction, Zn acts as the reductant while Cu²⁺ acts as the oxidant.

Question 3. Name some metals other than iron that can be extracted by thermite process.
Answer: Some metals other than iron that can be extracted from their oxides by thermite process are chromium (Cr), molybdenum (Mo), titanium (Ti), manganese (Mn) etc.

Question 4. Why is aluminium used in thermite process?
Answer: At high temperatures, aluminium exhibits strong reducing power, i.e., it has a strong affinity towards oxygen. For this reason, aluminium is used in thermite process.

Question 5. Name the element beiow which copper is placed in the metal activity series.
Answer: The element below which copper is placed in the metal activity series is hydrogen.

Question 6. Arrange Pb, Ca, Cu, Zn, Mg in increasing order of their reactivity.
Answer: Cu < Pb < Zn < Mg < Ca .

Question 7. Which metals are extracted , by carbon reduction method?
Answer: Metals which are placed in the middle region of the metal activity series are extracted by carbon reduction method.

Question 8. Arrange Na, Al, Fe, Pb in increasing order of their reducing power.
Answer: The increasing order of reducing power of the given elements is— Pb < Fe < Al < Nai.

Wbbse Class 10 Metallurgy Of Iron

Question 9. Between aluminium and tin, which one occupies a higher position in the metal activity series?
Answer: Aluminium occupies a higher position than tin in the metal activity series.

Question 10. Name a metal which reacts only with acids to produce hydrogen (H₂).
Answer: Tin (Sn) reacts only with acids to produce hydrogen (H₂).

Question 11. Give the equation of the reaction in which Mn+ ion is converted into metal M at the cathode during electrolysis of a fused salt containing Mn+ ion.
Answer: The equation is: Mⁿ⁺ + ne → M.

Question 12. What happens during the electrolytic reduction of fused NaCI?
Answer: During the electrolytic reduction of fused NaCI, Na is deposited at the cathode and CI₂ gas is liberated at the anode.

Question 13. Give example of a metal which can form H2 in reaction with steam.
Answer: Iron (Fe) forms H₂ in reaction with steam.

Question 14. Which one among Fe, Cu, Zn and Al does not form H₂ in reaction with dil H₂SO₄?
Answer: Cu is present in a lower position than H in metal activity series and thus does not form H₂ in reaction with dil. H₂SO_4.

Question 15. Write down the principle of Goldschmidt’s thermite process.
Answer: The fundamental principle of Goldschmidt’s thermite process is the reduction of the oxide of a less electropositive metal by another metal with higher electropositivity.

Question 16. Which substance is used as oxidant in thermite process?
Answer: Oxides of Fe, Cr, Mn etc., are used as oxidant in thermite process.

Question 17. Write down the reaction temperature of thermite process.
Answer: 2000°C.

Question 18. Write down an use of thermite process.
Answer: Thermite process is used in welding broken parts of heavy machineries, rail lines, tram lines, ships etc.

Question 19. Write down the equation of extraction of iron from red haematite by thermite process.
Answer:

\(\mathrm{Fe}_2 \mathrm{O}_3+2 \mathrm{Al} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{Fe}+\mathrm{Al}_2 \mathrm{O}_3\)

Wbbse Class 10 Metallurgy Of Iron

Question 20. Give example of two metals which cannot be extracted by carbon reduction process.
Answer: Sodium (Na) and aluminium (Al).

Question 21. Write down the general equation for carbon reduction process.
Answer:

\(\mathrm{MO}+\mathrm{C} \stackrel{\Delta}{\longrightarrow} \mathrm{M}+\mathrm{CO}(\mathrm{M}=\text { metal) }\)

Question 22. What is the name of the gas formed along with metals in carbon reduction process?
Answer: Carbon monoxide (CO).

Question 23. Which process of metal extraction is applied for the extraction of K, Ca, Na etc.?
Answer: Electrolytic process.

Question 24. In which electrode metal atoms are deposited in the electrolytic reduction method of metal extraction?
Answer: Cathode.

Question 25. Write down the name of two metals that can be extracted by electrolytic reduction method.
Answer: Aluminium (Al) and calcium (Ca).

Metallurgy Topic B Principles Of Metal Extraction And Oxidation-Reduction Fill In The Blanks:

Question 1. During electrolysis, metal cations move towards the cathode and get ______ by ______ accepting .
Answer: Reduced,electrons

Question 2. A metal oxide gets ______ removed from it.
Answer: Reduced

Question 3. On moving down the metal activity series, reducing power of the metals gradually _______
Answer: Decreases

Wbbse Class 10 Metallurgy Of Iron

Question 4. The extraction of a metal from the corresponding metal compound is always a ______ process.
Answer: Reduction

Question 5. The metal occupying the topmost position in the metal activity series is ______
Answer: Potassium

Question 6. _____ is also known as zinc white.
Answer: ZnO

Question 7. The constituents of thermite mixture are ______ and ______
Answer: Fe₂O₃, Al-powder

Question 8. Less reactive metals are found in nature in their ______ state.
Answer: Free

Question 9. In aqueous solution, a more reactive metal can ______ or _____ a less reactive metal from its salt.
Answer: Precipitate, reduce

Question 10. Metals placed at the top of the metal activity series have ______ affinity towards oxygen.
Answer: High

Question 11. In the metal activity series, Zn is placed_____ CU.
Answer: Above

Wbbse Class 10 Metallurgy Of Iron

Question 12. Among Fe, Cu, Zn and Al, ______ occupies the highest position in the metal activity series.
Answer: Al

Question 13. _____ dust is used as reductant in thermite process.
Answer: Aluminium

Question 14. Generally ______is used as reductant in carbon reduction process.
Answer: Coke

Question 15. Example of a metal that can be extracted by carbon reduction process is _____
Answer: Zinc

Question 16. The metal occupying the last position in the metal activity series is ______
Answer: Gold

Question 17. In the reaction, 2Fe³⁺ + Sn²⁺ → 2Fe²⁺ + Sn⁴⁺, Fe³⁺ acts as the ______ while Sn²⁺ acts as the ______
Answer: Oxidant, reductant

Metallurgy Topic B Principles Of Metal Extraction And Oxidation-Reduction State Whether True Or False:

Question 1. Fe can be extracted by thermite process.
Answer: True

Question 2. Metals placed at the top of the metal activity series are extracted by carbon reduction procedure.
Answer: False

Question 3. Metals placed at the top of the metal activity series are strong oxidising agent.
Answer: False

Question 4. Extraction of metal from ore is mainly oxidation.
Answer: False

Question 5. Thermite reaction is endothermic.
Answer: False

Question 6. Carbon is used as reductant in thermite process.
Answer: False

Question 7. Zinc cannot be extracted by carbon reduction process.
Answer: False

Question 8. Metals are obtained at cathode in electrolytic reduction process.
Answer: True

Metallurgy Topic C Corrosion Of Metals Synopsis:

1. If an iron object is left in moist air for a long time, then a reddish-brown layer of hydrated ferric oxide (Fe₂O₃ -xH₂O) is formed over the object at ordinary temperature which is commonly known as rust.
2. Rusting of iron is accelerated in the presence of ions like CI^–, SO₄^2- Thus, rusting becomes a major problem in case of ships and underground pipelines.
3. Some practical methods of preventing rusting of iron are—painting the surface of the iron object, coating the surface of the object with varnish, galvanisation or attaching a magnesium block to the iron object (sacrificial protection). Consequently, rusting of iron is prevented.
4. When an aluminium article comes in contact with moist air, a thin non-conducting layer of Al₂O₃ is formed over it, which protects it from further corrosion.
5. If copper objects are left in moist air for a long time, a green layer (basic copper carbonate) is formed over those objects.
6. Food items or fruits containing acids should not be stored or processed in containers made up of Al, Zn or Cu as it may lead to toxicity of food.

Metallurgy Topic C Corrosion Of Metals Short And Long Answer Type Questions:

Question 1. What is corrosion of metal?

Answer:

corrosion of metal:

When a piece of metal is kept in open air for a long time, the metal chemically reacts with atmospheric oxygen, CO₂  , water vapour etc., and is converted into other substances. As a result the metal piece erodes. This natural phenomenon is known as corrosion of metal.

Question 2. Why impure metals undergo quicker weathering as compared to the pure metals?

Answer: When a piece of impure metal is kept in open air, the impurities present in the metal acts as tiny electrochemical cells on the surface of the metal. Hence, it can be affected readily by atmospheric oxygen, water vapour etc. Pure metal generally does not form such cells and thus they are not weathered easily.

Question 3. What do you mean by rusting of iron? Why are metal articles corroded due to rusting?

Answer:

Rusting of iron:

1. When iron or iron objects are kept in moist air for a few days, a reddish brown layer of hydrated ferric oxide (Fe₂O₃-xH₂O) is formed over the objects. This reddish brown layer is called rust and the process is called rusting.
2. The volume of rust is generally greater than the volume of pure iron. Hence, after the formation of rust, the surface becomes flaky and comes out of the metal easily. Therefore, the objects undergo corrosion.

Question 4. Explain the mechanism of rusting.

Answer:

Mechanism of rusting

Rusting of iron is basically an electrochemical reaction. Due to the presence of impurities and rough surface, the oxidation of iron atoms do not take place uniformly. Some parts of iron gets readily oxidised than some other parts.

The part where oxidation takes place easily is called the anode region while the part where oxidation does not take place easily is called the cathode region. At anode region, Fe-atoms give up electrons and gets oxidised to Fe²⁺ ions which dissolve in water.

The released electrons move to the cathode region. At cathode region, O₂ dissolved in water accept these electrons and is reduced to water. The reduction takes place in presence of H⁺ ions that are obtained from the dissociation of carbonic add (H₂CO₃).

 

Anode reaction: \(2 \mathrm{Fe} \rightarrow 2 \mathrm{Fe}^{2+}+4 e\)

Cathode reaction: \(\begin{aligned}
& 4 \mathrm{H}^{+}+4 e \rightarrow 4 \mathrm{H} \\
& 4 \mathrm{H}+\mathrm{O}_2 \rightarrow 2 \mathrm{H}_2 \mathrm{O}
\end{aligned}\)

Net reaction: \(2 \mathrm{Fe}+\mathrm{O}_2+4 \mathrm{H}^{+} \rightarrow 2 \mathrm{Fe}^{2+}+2 \mathrm{H}_2 \mathrm{O}\)

Fe²⁺ ions produced at anode are further oxidised by aerial oxygen to form hydrated ferric oxide or rust (Fe₂O₃-xH₂O).

\(\begin{aligned}
& 4 \mathrm{Fe}^{2+}+\mathrm{O}_2+4 \mathrm{H}_2 \mathrm{O} \rightarrow 2 \mathrm{Fe}_2 \mathrm{O}_3+8 \mathrm{H}^{+} \\
& \mathrm{Fe}_2 \mathrm{O}_3+x \mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{Fe}_2 \mathrm{O}_3 \cdot x \mathrm{H}_2 \mathrm{O} \text { (rust) }
\end{aligned}\)

 

Question 5. What are the factors which accelerates the process of rusting?

Answer:

The process of rusting is accelerated by the following factors—

1. Presence of less electropositive metals in iron as impurity.
2. The presence of gases like CO₂, SO₂, SO₃, NO, NO₂ etc.
3. Presence of chloride (CI^–) or sulphate (SO₄^2- ) ions in water.

Question 6. Discuss the harmful effects of rusting.

Answer:

The harmful effects of rusting

1. Rusting affects the metallic lustre of iron.
2. Ironisusedtopreparesubstancesforhousehold works, transportation, agricultural and defence instruments. These substances corrode due to rusting causing huge economic losses.
3. Flouses, bridges etc. contain iron pillars. Similarly bodies of ships are made of iron. Rusting, makes them weak and brittle, which may lead to accidents.

Question 7. Why is rusting called “slow combustion’?

Answer: In the presence of aerial oxygen and water vapour, iron is oxidised to hydrated ferric oxide (Fe₂O₃ xH₂O) or rust. During this process, small amount of heat is also produced. Hence, it is sometimes called a ‘slow combustion’.

Question 8. Give some methods to prevent rusting of iron.

Answer:

Some methods to prevent rusting of iron

1. The iron articles can be protected from rusting by coating their surfaces with varnishes, paints or coal tar.
2. Rusting can be prevented by electroplating iron with zinc, tin or chromium.
3. When steam is passed over red hot iron, a thin layer of ferrosoferric oxide (Fe₃O₄) is formed on the surface of iron which protects it from rusting.
4. The underground oil pipelines through water, made of iron are protected by using Mg- blocks.

Question 9. Why do the oil or water pipelines through oceans and seas tend to form rust readily? How are they protected from rusting?

Answer:
1. Ocean and sea water contains dissolved chloride (CI^– ) and sulphate (SO₄^2-) ions. These ions facilitate the process of rusting. Hence, oil or water pipelines through oceans and seas tend to form rust readily.
2. To protect the underground or underwater pipelines from rusting, a block of more electropositive metal (like Mg) is connected to the pipe through an insultated wire. In this case, the iron pipes act as cathode, the magnesium block as anode and water as electrolyte. Magnesium being more reactive than iron is readily oxidised and hence prevents iron from rusting. The Mg block needs to be replaced after sometime as it corrodes gradually.

 

 

Question 10. Several magnesium blocks are attached to the bottom of ships. Why?

Answer:

Several magnesium blocks are attached to the bottom of ships.

The salty water of seas and oceans accelerates the process of rusting. The magnesium blocks attached to the bottom of the ships protect the iron parts of ships from rusting. Here, the ship acts as an electrochemical cell.

Mg is placed above iron in the metal activity series and hence, Mg acts as anode while iron acts as cathode. The salty water of ocean acts as an electrolytic solution. As oxidation takes place at anode, Mg is preferably oxidised to Mg²⁺ ions.

Thus iron remains unaffected as long as Mg blocks are present. New blocks replaces the already attached blocks that gets corroded.

Question 11. What do you mean by galvanisation?

Answer:

Galvanisation:

To protect iron from rusting and corrosion, sometimes a zinc coating is applied over iron objects mainly by electrolytic method. This is known as galvanisation. Iron coated with zinc is called galvanised iron.

Question 12. Why is zinc used in galvanisation to prevent rusting?

Answer: In the metal activity series zinc is placed above iron. Hence, zinc is more electropositive than iron and it is more easily oxidised than iron. So, when iron is coated with zinc, zinc is more readily affected by oxygen and water vapour. This protects iron from being oxidised. Thus, rusting is prevented.

Question 13. Zinc is more electropositive than iron, so it should be corroded more readily than iron. But, this doesn’t happen. Instead, zinc is coated over iron to prevent rusting. How will you explain this?

Answer: When zinc is exposed to air it is affected by oxygen, CO₂ and water vapour present in the air to form a layer of basic [Zn(OH)₂ • ZnCO₃].

This layer shields zinc from atmospheric air and hence further corrosion is prevented. This is why zinc is used to protect iron from rusting.

Question 14. Wilt it be justified to coat an iron cauldron/ used for cooking, with zinc to protect the cauldron from rusting?

Answer: The melting point of zinc is 420°C. while that of iron is 1525°C, i.e., zinc has a much lower melting point than iron. At about 250°C, zinc becomes brittle and the layer may break on application of higher temperature. Hence, it is not suitable to coat an iron cauldron, used for cooking, with zinc to protect the cauldron from rusting.

Question 15. To protect iron from rusting which one between zinc-plating and tin-plating is more effective and why?

Answer: When a crack on the surface of zinc-plated iron exposes the metallic iron, the metallic iron remains unaffected by the action of moist air and does not corrode. This is because, zinc is more reactive than iron(zinc is at higher position than iron in metal activity series) and hence zinc is affected by moist air more readily than iron.

On the other hand, any crack on the surface of tinplated iron which exposes iron makes the iron part vulnerable to rusting. This is because iron is more reactive than tin and hence iron is affected by moist air more readily than tin.This is why zinc-plating is more effective in preventing rust than tin-plating.

Question 16. Explain why tin-plated utensils are use- instead of zinc plated utensils to store food.

Answer: Zinc is more effective in preventing rusting and corrosion. Yet, tin-plated containers are more widely used to store food than zinc-plated containers because zinc may react with some acids present in food to produce toxic substances which may cause food poisoning. Tin does not produce such toxic substances. Hence, it is safer to use tinplated containers to store food.

Question 17. Why is aluminium protecting metal?

Answer:
1. When metallic aluminium is kept in moist air, it reacts oxygen and water vapour to form a nonconducting thin layer of aluminium oxide (Al₂O₃) over it’s surface. As a result, the metallic lustre is lost. But, the layer formed is in-soluble in water and protects the metal from further oxidation. Hence, corrosion of the metal is prevented. This is why aluminium is called a ‘self- protecting’ metal.

Question 18. Copper objects turn green when kept in air for a long time. Explain.

Answer:

Copper objects turn green when kept in air for a long time.

When exposed to moist air for a long period of time, copper is oxidised by aerial oxygen to copper oxide (CuO) which deposits on the surface of the object. Due to presence of H₂S in the air of industrial area, black layer of copper sulphide (CuS) is formed on the surface of the article. This layer is further oxidised to form green coloured basic copper sulphate [CuSO₄– 3Cu(OH)₂ ].

Sometimes, copper is also oxidised by O₂, CO₂ and water vapour to green coloured basic copper carbonate [CuCO₃ • Cu(OH)₂]. Due to the formation of these compounds, the object turns green.

 

Question 19. Copper vessels are sometimes cleaned with lemon or tamarind. What is the possible reason for this?

Answer:

Copper vessels are sometimes cleaned with lemon or tamarind

Copper vessels are oxidised by O₂, CO₂   and water vapour to form a thin layer of green-coloured basic copper carbonate [CuCO₃ • Cu(OH)₂] . Lemon or tamarind contains organic acids. These organic acids react with basic copper carbonate and remove the green patches. Hence; the green patch or stain gets removed from the vessels.

Question 20. Copper utensils which are not used fora long time should be used only after thorough cleaning—explain.

Answer:

Copper utensils which are not used fora long time should be used only after thorough cleaning

Green coating of basic copper carbonate is formed on copper utensils which are not used for a long time as a result of reaction of copper with atmospheric oxygen, carbon dioxide and water vapour, Basic copper carbonate is toxic in nature.

It causes toxicity if it is consumed along with food. Moreover, several micro-organisms which can cause diseases may be present on those utensils. That is why these copper utensils should be used only after thorough cleaning.

Question 21. Gold ornaments are often covered with green patches on their surfaces. Why?

Answer:

Gold ornaments are often covered with green patches on their surfaces

To increase the strength of gold for making ornaments, copper is added as an impurity. In moist air, this copper is slowly oxidised over a long period of time to form green coloured basic copper sulphate [CuSO_{4 •} Cu(OH)₂] or basic copper carbonate [CuCO₃ • Cu(OH)₂]. The green patches on the gold ornaments appears due to the formation of these compounds.

Question 22. Explain why it is harmful to eat pickles or chutneys kept in an aluminium foil.

Answer: Vinegar is generally used as an ingredient for making pickles or chutneys. Vinegar is nothing but an aqueous solution of acetic acid (CH₃COOH). Thus, it reacts with aluminium to form poisonous aluminium salt. Hence, it is harmful to eat pickles or chutneys kept in aluminium foil as it may cause food poisoning.

Question 23. Food or fruits haying sour taste should not be stored in containers made of aluminium, zinc or copper. Why?

Answer:

Food or fruits haying sour taste should not be stored in containers made of aluminium, zinc or copper.

Food or fruits having sour taste contains organic acids. These organic acids reacts with aluminium or zinc to form water soluble salts. Similarly, copper may also form water soluble salts with organic acids in the presence of oxygen. Some of the produced salts are toxic and may cause food poisoning. Hence, it is advisable not to store food or fruits having sour taste in containers made of aluminium, zinc or copper.

Metallurgy Topic C Corrosion Of Metals Very Short Answer Type Question Choose The Correct Answer:

Question 1. The chemical formula of rust is
1. FeO•xH₂O
2. Fe₂O₄
3. FeO₃
4. Fe₂O₃ •xH₂O

Answer: 4. Fe₂O₃ •xH₂O

Question 2. Presence of which of the following ions accelerates the process of rusting?
1. Na⁺
2. Ca²⁺
3. CI^– 
4. O^2-

Answer: 2. Ca²⁺

Question 3. Which of the following is used to protect the iron parts of ships from rusting?
1. Copper blocks
2. Aluminium blocks
3. Zinc blocks
4. Magnesium blocks

Answer: 4. Magnesium blocks

Question 4. Which of the following methods does not prevent rusting?
1. Painting the surface
2. Galvanisation
3. Using a Mg-block
4. Immersing in MgCl₂ solution

Answer: 4. Immersing in MgCl₂ solution

Question 5. During rusting, presence of which of the following ions in water causes the reduction of dissolved 02 ?
1. Fe²⁺ 
2. Fe³⁺ 
3. H⁺ 
4. Self-reduction occurs in this case

Answer: 3. H⁺ 

Question 6. To prevent rusting, Mg-block is attached to iron pipes because
1. Mg is more electropositive than Fe
2. Mg has a greater tendency to get oxidised than Fe
3. Both 1 and 2
4. None of these

Answer: 3. Both 1 and 2

Question 7. Galvanised iron is actually
1. Zn-coated iron
2. Sn-coated iron
3. Ni-coated iron
4. Cr-coated iron

Answer: 1. Zn-coated iron

Question 8. Green layer formed over copper and most of its alloys when exposed to moist air, is of
1. Basic copper nitrate
2. Acidic copper hydroxide
3. Basic copper carbonate
4. Acidic copper sulphate

Answer: 3. Basic copper carbonate

Question 9. Which of the following metals can protect itself from corrosion?
1. Al
2. Fe
3. Na
4. Cu

Answer: 1. Al

Physical Science Class 10 West Bengal Board

Question 10. The white layer formed over metallic aluminium in presence of moist air is of
1. AlCl₃
2. Al (OH)₃
3. Al₂O₃
4. AIN

Answer: 3. Al₂O₃

Question 11. Which metal protects itself by forming a coat of oxide?
1. Cu
2. Al
3. Fe
4. Zn

Answer: 2. Al

Question 12. Necessary component required for rust formation is
1. N₂ ,O₂
2. N₂ ,H₂ 
3. O₂,H₂O
4. CO₂, H₂O

Answer: 3. O₂,H₂O

Question 13. Which of the following is formed by the reaction of Al or Zn with organic acidic substances?
1. Soluble metallic salts
2. Insoluble metallic salts
3. Addition compound
4. Metallic hydroxides

Answer: 1. Soluble metallic salts

Physical Science Class 10 West Bengal Board

Question 14. Which of the following metals is used for galvanisation?
1. Fe
2. Ca
3. Zn
4. Mg

Answer: 3. Zn

Question 15. Rusting is a
1. Oxidation process
2. Reduction process
3. Redox process
4. Neutralisation reaction

Answer: 3. Redox process

Question 16. Rapid rusting of iron occurs in presence of Cl- because
1. Dissociation of water molecule increases
2. Dissociation of water molecule decreases
3. Chlorine gas reacts with iron
4. None of the above

Answer: 1. Dissociation of water molecule increases

Metallurgy Topic C Corrosion Of Metals Answer In Brief:

Question 1. Apart from aerial oxygen, which other component of the atmosphere is responsible for rusting of iron?
Answer: Apart from aerial oxygen, water vapour is responsible for rusting of iron.

Question 2. Which type of impurity facilitates the rusting of iron?
Answer: Presence of less electropositive metals in iron as impurities facilitates rusting.

Question 3. Name an electrochemical process.
Answer: Rusting of iron is an electrochemical process.

Question 4. Write the reactions that occur at the anode and cathode during rusting of iron.
Answer:
Anode reaction: \(2 \mathrm{Fe} \rightarrow 2 \mathrm{Fe}^{2+}+4 e\)

Cathode reaction: \(\mathrm{O}_2+4 \mathrm{H}^{+}+4 e \rightarrow 2 \mathrm{H}_2 \mathrm{O}\)

Question 5. Name a metal apart from zinc that can be used as a coating over iron to protect it from rusting?
Answer: Apart from zinc, tin can be used as a coating over iron to protect it from rusting.

Physical Science Class 10 West Bengal Board

Question 6. The presence of chloride ions facilitate rusting of iron. Mention one practical disadvantage of it.
Answer: Underwater pipelines made of iron are easily corroded by rusting due to the presence of CI^– ions in sea water.

Question 7. How can you protect iron from rusting?
Answer: If steam is passed over red hot iron, a thin layer of ferrosoferric oxide (Fe₃O₄) is formed over iron, which protects it from rusting.

Question 8. Write the composition of the green coloured layer formed on copper and most copper alloys when exposed to moist air for a long time.
Answer: Basic copper carbonate [CuCO₃-Cu(OH)₂].

Physical Science Class 10 West Bengal Board

Question 9. What are the necessary conditions required for rusting?
Answer: The process of rusting requires
1. Presence of atmospheric oxygen,
2. Presence of water vapour.

Question 10. Why does rusting not occur in pure iron?
Answer: Many electrochemical cells are formed on iron during rusting. In absence of impurities these cells cannot be formed and hence rust is not formed on pure iron.

Question 11. Presence of which ion accelerates rusting?
Answer: Presence of CI^– ion accelerates rusting.

Question 12. Why does rusting accelerate in presence of CO₂?
Answer: CO₂ forms carbonic acid by dissolving in water which increases the rate of dissociation of water. Hence rusting is accelerated.

Physical Science Class 10 West Bengal Board

Question 13. Name a process which protects iron from rusting.
Answer: Galvanisation.

Question 14. Which metal is used in galvanisation?
Answer: Zinc (Zn).

Question 15. What is “galvanised iron”?
Answer: Iron coated with metallic zinc is termed as ‘galvanised iron’ or G.l.

Question 16. Write down the advantage of galvanisation.
Answer: Galvanisation protects iron from rusting and corrosion.

Question 17. Which metal is used in cathodic protection of iron?
Answer: Magnesium is used in cathodic protection of iron.

Physical Science Class 10 West Bengal Board

Question 18. What is used as a suicidal electrode to prevent rust on a ship?
Answer: Magnesium block.

Question 19. What is passive iron?
Answer: A coating of iron oxide is formed over iron when it comes in contact with cone, nitric acid. This makes iron chemically inert and this type of iron is called passive iron.

Question 20. Which metal is called “self protecting metal”?
Answer: Aluminium is called ‘self protecting metal’.

Question 21. Which compounds are responsible for the formation of green coating on copper containers?
Answer: Basic copper carbonate [CuCO₃ • Cu(OH)₂] and basic copper sulphate [Cu SO₄ • 3Cu(OH)₂] .

Question 22. What is patina?
Answer: A green film of basic copper carbonate [Cu SO₄  • Cu(OH)₂] formed by the reaction of metallic copper with O₂, CO₂ and water vapour on the surface of copper made substances is called patina.

Question 23. Write down the formula of basic zinc carbonate.
Answer: ZnCO₃ • 3Zn(OH)₂ .

Physical Science Class 10 West Bengal Board

Metallurgy Topic C Corrosion Of Metals Fill In The Blanks:

Question 1. During rusting/oxygen dissolved in water gets reduced to form ______
Answer: H₂O

Question 2. Presence of ______ substances prevents rusting of iron.
Answer: Alkaline

Question 3. Rusting can be prevented if iron is kept in contact with _____ electropositive metals than iron.
Answer: More

Question 4. A thin non-conducting layer of _____ over Al prevents the metal from getting attacked by atmospheric 02 and moisture.
Answer: Al₂O₃

Question 5. Acidic food or fruits should not be kept in containers made of _____ or _____
Answer: Al, Zn

Physical Science Class 10 West Bengal Board

Question 6. Different weather conditions causes metallic objects to lose their ______
Answer: Lustre

Question 7. Rust do not occur in ______ iron.
Answer: Pure

Question 8. Rate of rusting _______ with increase in temperature.
Answer: Increase

Question 9. Process of coating ______ on iron substances is called galvanisation.
Answer: Zinc

Question 10. Mg-block attached with iron pipes for oil transportation, acts as _____
Answer: Anode

Question 11. The fine coating formed on Al metal in presence of moist air is of ______
Answer: Al₂O₃

Question 12. __________ coloured patches occur on copper containers if they are kept in opne air.
Answer: Green

Question 13. Due to formation of basic _____ in presence of moist air,zinc becomes faded.
Answer: Zinc carbonate

Question 14. Mg-blocks attached to underground pipes carrying oil act as the ______
Answer: Anode

Metallurgy Topic C Corrosion Of Metals State Whether True Or False:

Question 1. Cl ion accelerates the process of rusting.
Answer: True

Question 2. Objects made of copper turn green on prolonged exposure to air due to the formation of basic copper carbonate.
Answer: True

Question 3. It is justified to coat an iron cauldron used for cooking, with zinc to protect the cauldron from rusting.
Answer: False

Question 4. Ni-coated iron is known as galvanised iron.
Answer: False

Physical Science Class 10 West Bengal Board

Question 5. Chemical formula of rust formed on iron is FeO•x H₂O.
Answer: False

Question 6. Rusting occurs in the presence of water only.
Answer: False

Question 7. Pure metals are weathered more readily compared to impure metals.
Answer:False

Question 8. Rusting is a mild combustion.
Answer: True

Question 9. No atmospheric corrosion occurs aluminium if it is kept in open air.
Answer: True

Question 10. Aluminium pot is very useful for storing pickles and sauces.
Answer: False

Physical Science Class 10 West Bengal Board

Question 11. Sour fruits should not be kept cut in zinc coated containers.
Answer: True

Miscellaneous Type Questions Match The Column:

Question 1.

Column A	Column B
China clay	1. Ore of Cu
Magnetite	2. Ore of Zn
Calamine	3. Mineral of Al
Malachite	4. Mineral of Fe

 

Answer:
China clay: 3. Mineral of Al
Magnetite: 4. Mineral of Fe
Calamine: 2. Ore of Zn
Malachite: 1. Ore of Cu

Question 2.

Column A	Column B
K	1. Used to protect iron parts of ships from rusting
Zn	2. Reacts with both acid and base to produce H2
Au	3. Strong reducing agent
Mg	4. Obtained in free state in nature

 

Answer:
K: 3. Strong reducing agent
Zn: 2. Reacts with both acid and base to produce H₂
Au: 4. Obtained in free state in nature
Mg: 1. Used to protect iron parts of ships from rusting

Question 3.

Column A	Column B
Ca	1. Reacts with steam in red hot state to produce hydrogen
Pb	2. Reacts with cold water to produce hydrogen
Cu	3. Reacts only with acids to produce hydrogen
Zn	4. Does not produce hydrogen on reaction with acid

 

Answer:
Ca: 2. Reacts with cold water to produce hydrogen
Pb: 3. Reacts only with acids to produce hydrogen
Cu:  4. Does not produce hydrogen on reaction with acid
Zn:  1. Reacts with steam in red hot state to produce hydrogen

WBBSE Solutions for Class 10 Physical Science and Environment