Question 1

Which of the following best describes chemical equilibrium in a closed system?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

For the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$, which expression correctly represents the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = \frac{[NO_2$]^2}{[N_2O_4]}$$

Question 3

A mixture of $$\mathrm{N_2O_4}$$ and $$\mathrm{NO_2$} is $$placed in a sealed container and allowed to reach equilibrium. If more $$\mathrm{NO_2$} is $$added, what will happen according to Le Châtelier’s principle?

Accepted Answer

The system will shift to produce more $$\mathrm{N_2O_4}.$$

Question 4

Which of the following is true about the equilibrium constant $$K_c$$ for a reaction?

Accepted Answer

It is only affected by temperature.

Question 5

For the reaction $$\mathrm{2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)}$$, which of the following is the correct $$K_p$$ expression?

Accepted Answer

$$K_p = \frac{P_{SO_3$}^2}{P_{SO_2$}^2 P_{O_2$}}$$

Question 6

If $$K_c$$ for a reaction is very large ($$K_c \gg 1$$), what does this indicate about the position of equilibrium?

Accepted Answer

The reaction mixture contains mostly products at equilibrium.

Question 7

Which of the following changes will NOT affect the position of equilibrium for a gaseous reaction?

Accepted Answer

Adding an inert gas at constant volume.

Question 8

For the reaction $$\mathrm{CH_4$(g) + H_2O(g) \rightleftharpoons CO(g) + 3H_2(g)}$$, what is the correct equilibrium constant expression $$K_c$$?

Accepted Answer

$$K_c = \frac{[CO][H_2$]^3}{[CH_4$][H_2O]}$$

Question 9

Which equation relates the equilibrium constant $$K_p to$$ $$K_c$$ for a reaction involving gases?

Accepted Answer

$$K_p = K_c (RT$$)^{\Delta n}$$

Question 10

A reaction mixture at equilibrium is disturbed by increasing the temperature for an endothermic reaction. What will happen to the equilibrium position?

Accepted Answer

It will shift towards the products.

Question 11

For the reaction $$\mathrm{2NO_2(g) \rightleftharpoons N_2O_4(g)}$$, if the volume of the container is decreased, what will happen to the equilibrium position?

Accepted Answer

It will shift towards the side with fewer moles of gas.

Question 12

Which of the following is true about the effect of a catalyst on a chemical equilibrium?

Accepted Answer

It speeds up the attainment of equilibrium but does not change the equilibrium position.

Question 13

Given the reaction $$\mathrm{CO_2$(g) + H_2O(l) \rightleftharpoons H_2CO_3(aq)}$$, which species are omitted from the equilibrium constant expression?

Accepted Answer

H$$_2O(l)$$

Question 14

For the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, what is the value of $$\Delta n$$ used in the $$K_p$$ and $$K_c$$ relationship?

Accepted Answer

$$\Delta n = -2$$

Question 15

Which of the following correctly describes the relationship between Gibbs free energy and the equilibrium constant?

Accepted Answer

$$\Delta G^\circ = -RT \ln K$$

Question 16

If $$Q \u003c K$$ for a reaction mixture, what will happen as the system moves towards equilibrium?

Accepted Answer

The reaction will shift towards the products.

Question 17

Which of the following is the correct equilibrium constant expression for the heterogeneous reaction $$\mathrm{$$CaCO_3$$(s) \rightleftharpoons CaO(s) + CO_2$(g)}$$?

Accepted Answer

$$K_c = [CO_2$]$$

Question 18

If the coefficients in a balanced chemical equation are multiplied by 2, how does the equilibrium constant $$K$$ change?

Accepted Answer

It is squared.

Question 19

For the reaction $$\mathrm{2NO(g) + O_2$(g) ightleftharpoons 2NO_2(g)}$$, if the equilibrium constant $$K_c is$$ $$1.4 	imes 10^6$ at 227°C, what does this indicate about the reaction mixture at equilibrium?

Accepted Answer

Mostly products are present.

Chemical Equilibrium: Principles, Calculations, and Applications

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