WBBSE Solutions For Class 8 School Science Chapter 2 Element Compound And Chemical Reaction Review Questions

Chapter 2 Element Compound and Chemical Reaction MCQs

 

Question 1. The enzymes are basically

  1. Carbohydrates
  2. Proteins
  3. Fats
  4. Minerals

Answer: 2. Proteins

Question 2. The catalyst used to prepare ammonia from nitrogen and hydrogen is

  1. Vanadium pentoxide
  2. Iron powder
  3. Zinc powder
  4. Molybdenum

Answer: 2. Iron powder

Question 3. The catalyst used to prepare s03 from sO2 and oxygen is

  1. Vanadium pentoxide
  2. Hydrogen peroxide
  3. Manganese dioxide
  4. Red hot iron

Answer: 2. Hydrogen peroxide

Read And Learn More WBBSE Solutions For Class 8 School Science Review Questions

Question 4. The enzyme pepsin is found in our

  1. Liver
  2. Stomach
  3. Intestine
  4. Gall bladder

Answer: 2. Stomach

Question 5. Which one is not correct?

  1. The catalyst influences the rate of reaction but does not participate in the reaction
  2. There is no universal catalyst which can enhance the rate of all the reactions.
  3. A suitable catalyst for a specific reaction can only be found by proper experimentation.
  4. A powdered catalyst is more effective than a solid one due to increased surface area.

Answer: 1. Catalyst influences the rate of reaction but does not participate in the reaction

Question 6. The enzyme invertase

  1. Converts proteins into smaller amino acids
  2. Converts sucrose to glucose and fructose
  3. Decomposes hydrogen peroxide
  4. Hydrolyses lipid

Answer: 2. Converts sucrose to glucose and fructose

Question 7. When rusting occurs, the weight of iron

  1. Increases
  2. Decreases
  3. Remains unchanged
  4. None of these

Answer: 1. Increases

Question 8. Potassium permanganate is

  1. An enzyme
  2. A reducing agent
  3. An oxidizing agent
  4. A corrosive agent

Answer: 3. An oxidizing agent

Question 9. formation of ammonia from nitrogen and hydrogen is

  1. An exothermic reaction
  2. An endothermic reaction
  3. Not influenced by catalyst
  4. None of these

Answer: 1. An exothermic reaction

Question 10. for rusting of iron

  1. Moist air is required
  2. Only water is required
  3. Only oxygen is required
  4. Nothing is required

Answer: 1. Moist air is required

Question 11. the activity of a catalyst is enhanced depending upon

  1. Its volume
  2. It’s mass
  3. It’s the surface area
  4. Its density

Answer: 3. It’s the surface area

Question 12. An example of an inorganic solvent is

  1. Benzene
  2. Water
  3. Toluene
  4. Kerosene

Answer: 2. Water

Question 13. A catalyst

  1. Is required in a large amount
  2. Cannot initiate a reaction
  3. Cannot influence the rate of a reaction
  4. Is consumed in the reaction

Answer: 2. Cannot initiate a reaction

Question 14. Reduction involves

  1. Addition of oxygen or chlorine
  2. Removal of hydrogen
  3. De-electronation
  4. Electronation

Answer: 4. Electronation

Question 15. \(\mathrm{Fe}_2 \mathrm{O}_3+3 \mathrm{C} \rightarrow 2 \mathrm{Fe}+3 \mathrm{CO}\)  in this reaction,

  1. Fe undergoes oxidation and c undergoes reduction
  2. Both fe and c undergo oxidation
  3. Both fe and c undergo a reduction
  4. Fe undergoes reduction and c undergoes oxidation

Answer: 4. Fe undergoes reduction and c undergoes oxidation

Question 16. rusting of iron is an example of

  1. Oxidation and displacement reaction
  2. Reduction and combination reaction
  3. Oxidation and combination reaction
  4. Reduction and displacement reaction

Answer: 3. Oxidation and combination reaction

Question 17. The same substance which can act both as an oxidant and reductant is

  1. K2cr207
  2. H2O2
  3. Co
  4. FecI3

Answer: 2. H2O2

Chapter 2 Element Compound And Chemical Reaction Chemical Reaction Match The Columns

 

Column – A Column – B
A. Urease 1.  Converts proteins into smaller amino acids
B. Pepsin 2. Hydrolysis of urea
C. Catalase 3.  Conversion of sucrose into glucose and fructose
 D. Invertase 4. Decomposition of H2O2

Answer: A-2,B-1,C-4,D-3

Column – A Column – B
A.  Oxidation 1. Gain of electron
B. Reduction 2. Negative catalyst in the decomposition of H2O2
C.  Rusting 3. Loss of electrons
D. H3PO4 4.  Oxidation

Answer: A-3,B-1,C-4,D-2

 

Chapter 2 Element Compound And Chemical Reaction Chemical Reaction Fill In The Blanks

 

Question 1. Combustion of methane is an __________ reaction.
Answer: Oxidation

Question 2. In a redox reaction, oxidising agent (or oxidant) is __________.
Answer: Reduced

Question 3. In a redox reaction, oxidising agent (or oxidant) accepts __________.
Answer: Electrons

Question 4. In a redox reaction, a reducing agent (or reductant) __________ electron (s).
Answer: Losses

Question 5. In a redox reaction, a reducing agent (reductant) is __________ (i.e., converted to oxidized species).
Answer: Oxidized

Question 6. Increasing the temperature increases the __________ energy of the molecules.
Answer: Kinetic

Question 7. “Like dissolves __________”.
Answer: Like

Question 8. An article made of iron is coated with a thin __________
Answer: Electroplating

Question 9. The enzyme __________ decomposes hydrogen peroxide (H2O2) to water and oxygen.
Answer: Catalase

Question 10. Arhar daal and watermelon seeds contain the enzyme __________
Answer: Urease

Question 11. The enzyme, __________ is found in the fresh potato.
Answer: Catalase

Question 12. __________ reaction is a chemical reaction in which chlorine is added.
Answer: Oxidation

Question 13. __________ is a chemical reaction in which the addition of hydrogen occurs with an element or a compound.
Answer: Reduction

Question 14. Oxidation is defined as a chemical reaction involving __________ of electrons from an atom or ion.
Answer: Loss

Question 15. Reduction is a chemical reaction involving __________ of an electron by an atom or ion.
Answer: Gain

Question 16. __________ acts as a catalyst in the decomposition of H2O2 into Oxygen and water
Answer: MnO2

 

Chapter 2 Element Compound And Chemical Reaction Chemical Reaction Identify As ‘True Or False

Question 1. If the temperature is increased, the kinetic energy of the molecules increases.
Answer: True

Question 2. Rusting is basically a reduction of iron.
Answer: False

Question 3. When an atom loses an electron(s), it is oxidized.
Answer: True

Question 4. Water acts as a solvent in many chemical reactions.
Answer: True

Question 5. The choice of catalyst for a particular chemical reaction can only be determined by performing the experiments only. It cannot be predicted.
Answer: True

Question 6. In the case of a solid catalyst, when it is crushed, its surface area decreases.
Answer: False

Question 7. As the surface area of a solid catalyst increases, the rate of the reaction decreases.
Answer: False

Question 8. The combustion of fossil fuel is an example of an oxidation reaction.
Answer: True

Question 9. Photosynthesis requires sunlight.
Answer: True

Question 10. Oxidation and reduction cannot occur simultaneously in a chemical reaction.
Answer: False

Question 11. \( \mathrm{Cu}^{2+}+2 \mathrm{e} \rightarrow \mathrm{Cu} .\) This is an oxidation reaction.
Answer: False

Question 12. Enzymes are biological molecules that act as catalysts and help complex reactions to occur.
Answer: True

Question 13. The enzymes are basically proteins.
Answer: True

Question 14. Trypsin is found in our intestines.
Answer: True

Question 15. Pepsin converts proteins into smaller amino acids in our stomach.
Answer: True

Question 16. An oxidation reaction is a chemical reaction in which chlorine is added.
Answer: True

Question 17. In a redox reaction, oxidising agent (or oxidant) accepts electron(s) and is reduced (i.e., converted to reduced species).
Answer: True

Question 18. In a redox reaction, a reducing agent (or reductant) loses an electron(s) and is oxidized (i.e., converted to oxidized species).
Answer: True

Question 19. When metallic iron is exposed to moist air, rusting of iron occurs.
Answer: True

Question 20. Endothermic reactions are responsible for explosive reactions.
Answer: False

 

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