Equilibrium NEET MCQ

1. Which statement correctly defines dynamic equilibrium?

a) The rate of the forward reaction is zero.
b) The rate of the reverse reaction is zero.
c) The concentrations of reactants and products remain constant.
d) The reaction has reached completion.

Answer:

c) The concentrations of reactants and products remain constant.

Explanation:

In dynamic equilibrium, forward and reverse reactions continue, but there's no net change in concentration.

2. The equilibrium constant for a reaction is 1. What does this signify?

a) The reaction is incomplete.
b) The concentrations of reactants and products are equal at equilibrium.
c) The forward reaction is favored.
d) The reverse reaction is favored.

Answer:

b) The concentrations of reactants and products are equal at equilibrium.

Explanation:

A K value of 1 means the ratio of products to reactants is equal.

3. For the reaction A + B ⇌ C + D, which expression is the correct equilibrium constant?

a) [A][B] / [C][D]
b) [C][D] / [A][B]
c) [A] + [B] / [C] + [D]
d) [C] + [D] / [A] + [B]

Answer:

b) [C][D] / [A][B]

Explanation:

The equilibrium constant is the ratio of the concentration of products to reactants.

4. In which case will the value of K and Q be the same?

a) At equilibrium
b) At the beginning of the reaction
c) At the completion of the reaction
d) Never

Answer:

a) At equilibrium

Explanation:

At equilibrium, the reaction quotient (Q) becomes equal to the equilibrium constant (K).

5. If Q > K for a reaction, then:

a) The reaction will proceed in the forward direction.
b) The reaction will proceed in the reverse direction.
c) The reaction is at equilibrium.
d) The direction cannot be determined.

Answer:

b) The reaction will proceed in the reverse direction.

Explanation:

If Q > K, there are too many products, so the reaction will shift towards reactants.

6. A catalyst added to a reaction at equilibrium:

a) Shifts the equilibrium to the right.
b) Shifts the equilibrium to the left.
c) Increases the value of the equilibrium constant.
d) Does not affect the position of equilibrium.

Answer:

d) Does not affect the position of equilibrium.

Explanation:

Catalysts speed up both forward and reverse reactions equally, without changing the equilibrium position.

7. Le Chatelier’s principle states:

a) Equilibrium is dynamic in nature.
b) At equilibrium, Q = K.
c) If a system at equilibrium is disturbed, it will shift to counteract the disturbance.
d) Equilibrium reactions go to completion.

Answer:

c) If a system at equilibrium is disturbed, it will shift to counteract the disturbance.

Explanation:

Le Chatelier’s principle describes how equilibria respond to disturbances.

8. For a gaseous reaction at equilibrium, if the volume is decreased:

a) The side with fewer moles of gas will be favored.
b) The side with more moles of gas will be favored.
c) The equilibrium constant will increase.
d) Equilibrium will not be affected.

Answer:

a) The side with fewer moles of gas will be favored.

Explanation:

A decrease in volume increases pressure, shifting equilibrium to the side with fewer gas moles.

9. Which will not change the value of the equilibrium constant?

a) Change in concentration
b) Change in temperature
c) Addition of a catalyst
d) Change in pressure

Answer:

c) Addition of a catalyst

Explanation:

Only a change in temperature alters the equilibrium constant. Catalysts affect the rate but not the K value.

10. For an exothermic reaction, if the temperature is increased:

a) K will increase.
b) K will decrease.
c) The reaction will not reach equilibrium.
d) The equilibrium position remains unchanged.

Answer:

b) K will decrease.

Explanation:

For exothermic reactions, increasing temperature favors the reverse reaction, decreasing K.

11. Which of the following statements about equilibrium is FALSE?

a) At equilibrium, the concentrations of reactants and products remain constant.
b) Equilibrium can only be achieved in closed systems.
c) At equilibrium, the forward reaction rate equals the reverse reaction rate.
d) Equilibrium implies that all reactants have been converted to products.

Answer:

d) Equilibrium implies that all reactants have been converted to products.

Explanation:

Equilibrium means the rate of forward reaction equals the rate of the reverse reaction, not the completion of a reaction.

12. A reaction has an equilibrium constant K = 10^(-5). This indicates:

a) The reaction strongly favors the reactants.
b) The reaction strongly favors the products.
c) The reaction goes to completion.
d) The reaction does not occur.

Answer:

a) The reaction strongly favors the reactants.

Explanation:

A small K value indicates a higher concentration of reactants compared to products at equilibrium.

13. Which change will NOT shift the equilibrium of a reaction?

a) Addition of a non-reacting gas.
b) Increase in temperature.
c) Addition of a catalyst.
d) Change in concentration of a reactant.

Answer:

a) Addition of a non-reacting gas.

Explanation:

Adding a non-reacting gas does not affect the partial pressures or concentrations of the reacting species.

14. The reaction quotient Q is calculated the same way as K, but:

a) Only for reactions at equilibrium.
b) Only for reactions not at equilibrium.
c) Only for endothermic reactions.
d) Only for exothermic reactions.

Answer:

b) Only for reactions not at equilibrium.

Explanation:

Q is calculated using current concentrations, regardless of whether the system is at equilibrium.

15. For the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g), if the pressure is increased:

a) Equilibrium shifts to the right.
b) Equilibrium shifts to the left.
c) No effect on equilibrium.
d) The reaction goes to completion.

Answer:

a) Equilibrium shifts to the right.

Explanation:

Increasing the pressure will favor the side with fewer moles of gas.

16. Which factor does NOT affect the value of the equilibrium constant (K)?

a) Temperature
b) Pressure
c) Concentration
d) Catalysts

Answer:

d) Catalysts

Explanation:

Catalysts only affect the rate of the reaction, not the position of equilibrium.

17. The presence of a catalyst in a reaction at equilibrium:

a) Increases the value of K.
b) Decreases the value of K.
c) Shifts the equilibrium to the left.
d) Does not shift the equilibrium position.

Answer:

d) Does not shift the equilibrium position.

Explanation:

Catalysts only affect the rate of reactions and don't change the position of equilibrium.

18. An increase in temperature for an endothermic reaction:

a) Increases the value of K.
b) Decreases the value of K.
c) Does not affect K.
d) Shifts the equilibrium to the left.

Answer:

a) Increases the value of K.

Explanation:

For endothermic reactions, increasing temperature favors the forward reaction, increasing K.

19. A reaction that is slow to reach equilibrium:

a) Has a large K value.
b) Has a small K value.
c) Has a high activation energy.
d) Always favors the products.

Answer:

c) Has a high activation energy.

Explanation:

The speed to reach equilibrium is affected by the activation energy, not the value of K.

20. For a reaction at equilibrium, a decrease in volume will:

a) Always shift the equilibrium to the right.
b) Always shift the equilibrium to the left.
c) Shift the equilibrium to the side with fewer moles of gas.
d) Not affect the equilibrium.

Answer:

c) Shift the equilibrium to the side with fewer moles of gas.

Explanation:

A decrease in volume increases the pressure, and the system will shift to the side with fewer moles of gas to counteract the change.

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