Question 1

Which of the following best describes a chemical equilibrium?

Accepted Answer

A dynamic state where the rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant.

Question 2

For the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, which of the following is the correct equilibrium constant expression in terms of concentration?

Accepted Answer

$$K_c = \frac{[NH_3$]^2}{[N_2$][H_2$]^3}$$

Question 3

A reaction mixture initially contains only reactants. As the reaction proceeds toward equilibrium, what happens to the concentrations of reactants and products?

Accepted Answer

Reactant concentrations decrease, product concentrations increase until equilibrium is reached.

Question 4

Given the following reaction at equilibrium: $$\mathrm{2NO_2(g) \rightleftharpoons N_2O_4(g)}$$, if the concentration of $$\mathrm{NO_2$} is $$increased, what will happen according to Le Châtelier's principle?

Accepted Answer

The equilibrium will shift to the right, forming more $$\mathrm{N_2O_4}.$$

Question 5

For the reaction $$\mathrm{H_2O(l) \rightleftharpoons H_2O(g)} at $$equilibrium in a closed container, which of the following statements is true?

Accepted Answer

The rate of evaporation equals the rate of condensation.

Question 6

Which of the following is NOT included in the equilibrium constant expression for the reaction $$\mathrm{$$CaCO_3$$(s) \rightleftharpoons CaO(s) + CO_2$(g)}$$?

Accepted Answer

$$[$$CaCO_3$$]$$

Question 7

If the equilibrium constant $$K_c$$ for a reaction is much greater than 1, what does this indicate about the equilibrium mixture?

Accepted Answer

The mixture contains mostly products.

Question 8

For the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$, $$K_c = 0.212 at a $$certain temperature. What is the value of $$K_c$$ for the reverse reaction $$\mathrm{2NO_2(g) \rightleftharpoons N_2O_4(g)}$$?

Accepted Answer

$$\frac{1}{0.212}$$

Question 9

A reaction at equilibrium is subjected to an increase in pressure by decreasing the volume. Which direction will the equilibrium shift for the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$?

Accepted Answer

Toward the side with fewer moles of gas.

Question 10

Which of the following changes will NOT affect the value of the equilibrium constant $$K$$ for a given reaction?

Accepted Answer

Adding a catalyst.

Question 11

For the reaction $$\mathrm{2SO_2(g) + O_2$(g) ightleftharpoons 2SO_3(g)}$$, the equilibrium constant $$K_c is$$ $$4.0 	imes 10$$^{24}$$ at 25°C. What does this imply about the reaction mixture at equilibrium?

Accepted Answer

The mixture contains almost only $$\mathrm{SO_3$}.$$

Question 12

Given the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, if the temperature is increased and the reaction is exothermic, what will happen to the equilibrium position?

Accepted Answer

It will shift toward the reactants.

Question 13

For the reaction $$\mathrm{2A \rightleftharpoons B}$$, the equilibrium constant is $$K_1. $$What is the equilibrium constant for the reaction $$\mathrm{6A \rightleftharpoons 3B}$$?

Accepted Answer

$$K_1^3$

Question 14

A mixture at equilibrium contains $$[A] = 0.20\ \mathrm{M}$$, $$[B] = 0.10\ \mathrm{M}$$, and $$[C] = 0.40\ \mathrm{M}$$ for the reaction $$\mathrm{A + 2B \rightleftharpoons C}. $$What is the value of $$K_c$$?

Accepted Answer

$$K_c = \frac{[C]}{[A][B]^2}$$

Question 15

For the reaction $$\mathrm{H_2O(l) \rightleftharpoons H_2O(g)}$$, which of the following is the correct expression for the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = [H_2O(g)]$$

Question 16

A closed system at equilibrium for the reaction $$\mathrm{A(g) \rightleftharpoons B(g)} is $$disturbed by removing some $$\mathrm{B}. $$What will happen?

Accepted Answer

The equilibrium will shift to the right to produce more $$\mathrm{B}.$$

Question 17

For the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$, if the partial pressure of $$\mathrm{N_2O_4} is$$ $$0.0145\ \mathrm{atm}$$ and the partial pressure of $$\mathrm{NO_2$} is$$ $$0.0761\ \mathrm{atm} at $$equilibrium, what is the value of $$K_p$$?

Accepted Answer

$$K_p = \frac{(0.0761)^2$}{0.0145}$$

Question 18

Which of the following best explains why solids and pure liquids are not included in equilibrium constant expressions?

Accepted Answer

Their concentrations do not change during the reaction.

Question 19

A reaction mixture at equilibrium is subjected to a decrease in temperature. The reaction is endothermic. What will happen to the equilibrium position?

Accepted Answer

It will shift toward the reactants.

Chemical Equilibria: Principles, Calculations, and Applications

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