MCQ Questions

Question No. 1

Match the terms in Column B with the descriptions in Column A.

Answer :

a) Collision frequency

b) Activated complex

c) Reaction rate

d) Activation energy

e) Collision theory

Question No. 2

Zinc pieces (3.0 g) react with 50 cm³ of 0.2 mol·dm⁻³ hydrochloric acid according to the equation Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g). How would the rate of reaction compare to the reaction above if:

Answer :

a) 3.0 g of zinc powder were used, instead of 3.0 g of zinc pieces?

b) the concentration of hydrochloric acid used were changed to 0.1 mol·dm⁻³?

c) a suitable catalyst were used?

d) the temperature were increased?

e) 100 cm³ of the 0.2 mol·dm⁻³ hydrochloric acid were used?

Question No. 3

The following chemical reaction has reached dynamic equilibrium in a closed container: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) + heat.

Answer :

a) What does ΔH mean?

b) What does the symbol ⇌ mean?

c) What is chemical equilibrium?

d) Is the forward reaction exothermic or endothermic?

e) Is the reverse reaction exothermic or endothermic?

f) Explain why a closed container is used for this chemical reaction.

Question No. 4

Write down the Kc expressions for each of the following equilibria:

Answer :

d) 2H₂(g) + O₂(g) ⇌ 2H₂O(g)

a) 2NO₂(g) + O₂(g) ⇌ 2NO₃(g)

b) COCl₂(g) ⇌ CO(g) + Cl₂(g)

c) C(s) + CO₂(g) ⇌ 2CO(g)

Question No. 5

When hydrogen reacts with iodine at 700 K in a closed container, the following equilibrium is established: H₂(g) + I₂(g) ⇌ 2HI(g). Analysis of the equilibrium mixture at 700 K showed that: [H₂] = 1.84×10⁻³ mol·dm⁻³, [I₂] = 3.13×10⁻³ mol·dm⁻³, [HI] = 17.7×10⁻³ mol·dm⁻³.

Answer :

a) Is this a homogeneous or heterogeneous equilibrium? Explain.

b) Calculate the equilibrium constant (Kc) for this reaction at 700 K.

c) The pressure on the system is increased. Explain the effect that this change in pressure would have on the equilibrium position and rate of reaction.

Question No. 6

Three moles of N₂(g) are placed in a 2 dm³ container with 8 mol H₂(g) and the reaction proceeds until equilibrium is reached at 450 °C: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) ΔH < 0. At equilibrium, 4 mol NH₃(g) is present. Calculate the Kc value.

Answer :

Question No. 7

Consider the following equilibrium situation: CO₂(g) + H₂(g) ⇌ H₂O(g) + CO(g) ΔH > 0.

Answer :

a) State Le Châtelier’s Principle.

b) What would the effect on the equilibrium position be if the temperature in the container were decreased? Explain.

c) What would the effect on the equilibrium position be if the concentration of CO₂(g) in the container were increased? Explain.

Question No. 8

Which of the following factors would not affect the rate of a chemical reaction?

Answer :

A. Physical states of reactants

B. Change in temperature of the reaction system

C. Density of the reactants

D. Addition of a catalyst

Question No. 9

This factor will affect the equilibrium constant value:

Answer :

A. Concentration

B. Pressure

C. Temperature

D. Catalyst

Question No. 10

Which factor will not affect the chemical equilibrium?

Answer :

A. Temperature

B. Catalyst

C. Pressure

D. Concentration

Chapter

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