9th class Chemistry, Chapter 6: Equilibria MCQs

1. What will happen if the rates of forward and reverse reactions are very high?

1. (A) The equilibrium point will reach very soon. ✓
2. (B) The equilibrium point will reach very late.
3. (C) The reaction will not attain the state of dynamic equilibrium.
4. (D) The reaction will be practically irreversible.

2. Predict which components of the atmosphere react in the presence of lightning.

1. (A) N₂ and H₂O
2. (B) O₂ and H₂O
3. (C) CO₂ and O₂
4. (D) N₂ and O₂ ✓

3. An inorganic chemist places one mole of PCl₅ in a container A and one mole of each Cl₂ and PCl₃ in container B. Both the containers were sealed and heated to the same temperature to reach the state of equilibrium. Guess about the composition of mixtures in both the containers.

1. (A) Both the containers will have the same composition of mixtures. ✓
2. (B) Container A will have more concentration of PCl₅ than B.
3. (C) Container A will have less concentration of PCl₅ than B.
4. (D) Both the containers will have zero concentration of its reactants.

4. CaO or lime is used extensively in steel, glass and paper industries. It is produced in an exothermic reversible reaction by the decomposition of lime (CaCO₃). Choose the conditions to produce maximum amount of lime.

1. (A) Heating at high temperature in a closed vessel
2. (B) Heating at high temperature in an open vessel ✓
3. (C) Cooling it in a closed vessel
4. (D) Cooling it in an open vessel

5. What condition should be met for the reversible reaction to achieve the state of equilibrium?

1. (A) All the reactants should be converted into the products.
2. (B) 50% of the reactants should be converted into products.
3. (C) The concentrations of all the reactants and the products should become constant. ✓
4. (D) One of the products should be removed from the reaction mixture.

6. Why the gas starts coming out when you open a can of fizzy drink?

1. (A) Because the solubility of the gas increases
2. (B) Because the gas is insoluble in water
3. (C) Because the gas is dissolved under pressure hence it comes out when pressure is decreased ✓
4. (D) Because the solubility of the gas decreases at high pressure

7. The following reaction is performed in a closed vessel: CaCO₃(s) ⇌ CaO(s) + CO₂(g). How the equilibrium will be affected if you increase the pressure?

1. (A) The forward reaction will be favoured
2. (B) The backward reaction will be favoured ✓
3. (C) No effect on backward reaction
4. (D) No effect on forward or backward reaction

8. When a reaction will become a reversible one?

1. (A) If the activation energy of the forward reaction is comparable to that of backward reaction ✓
2. (B) If the activation energy of the forward reaction is higher than that of backward reaction
3. (C) If the activation energy of the forward reaction is lower than that of backward reaction
4. (D) If the enthalpy change of both the reactions is zero.

9. Is reversible reaction useful for preparing compounds on large scale?

1. (A) No
2. (B) Yes ✓
3. (C) They are useful only when equilibrium lies far to the right side
4. (D) They are useful only when equilibrium lies far to the left side

10. What will happen to the concentrations of the products if a reversible reaction at equilibrium is not disturbed?

1. (A) They will remain constant ✓
2. (B) They will keep on increasing
3. (C) They will keep on decreasing
4. (D) They will remain constant for some time and then start decreasing

11. A reaction which moves in the forward direction only and goes to completion is called:

1. (A) Reversible reaction
2. (B) Equilibrium reaction
3. (C) Endothermic reaction
4. (D) Irreversible reaction ✓

12. The reaction NaCl(aq) + AgNO₃(aq) → AgCl(s) + NaNO₃(aq) is:

1. (A) At equilibrium
2. (B) Endothermic
3. (C) Irreversible ✓
4. (D) Reversible

13. A reversible reaction is shown by the symbol:

1. (A) ⇌ ✓
2. (B) →
3. (C) =
4. (D) ↑

14. The formation of ammonia (N₂ + 3H₂ ⇌ 2NH₃) is carried out at:

1. (A) 100 °C and 1 atm with Ni
2. (B) 25 °C and 200 atm with Pt
3. (C) 1000 °C without catalyst
4. (D) 400 °C and 200 atm with Fe ✓

15. Heating CaCO₃ in an open container goes to completion because:

1. (A) CaO melts
2. (B) CaCO₃ is a gas
3. (C) A catalyst is present
4. (D) CO₂ escapes into the atmosphere ✓

16. Hydrated copper sulphate (CuSO₄·5H₂O) is:

1. (A) White
2. (B) Pink
3. (C) Green
4. (D) Blue ✓

17. Anhydrous cobalt chloride is:

1. (A) Blue ✓
2. (B) Pink
3. (C) Purple
4. (D) White

18. Cobalt chloride dihydrate (CoCl₂·2H₂O) is:

1. (A) Pink
2. (B) Blue
3. (C) White
4. (D) Purple ✓

19. A reversible reaction is at chemical equilibrium when:

1. (A) All reactants are used up
2. (B) The backward reaction stops
3. (C) The rate of forward reaction equals the rate of backward reaction ✓
4. (D) The forward reaction stops

20. Chemical equilibrium is called dynamic because:

1. (A) The reaction stops completely
2. (B) Concentrations keep changing
3. (C) Only the forward reaction goes on
4. (D) Both reactions keep on going ✓