Question 1

Which statement best describes chemical equilibrium in a closed system?

Accepted Answer

The rates of the forward and reverse reactions are equal, and the concentrations of reactants and products remain constant.

Question 2

For the reaction $\mathrm{N_2O_4(g) \rightleftharpoons 2 NO_2(g)}$, what is the correct equilibrium constant expression ($K_c$)?

Accepted Answer

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

Question 3

In the Haber process, $\mathrm{N_2(g) + 3 H_2(g) \rightleftharpoons 2 NH_3(g)}$, how does increasing the pressure affect the equilibrium position?

Accepted Answer

It shifts the equilibrium toward the products.

Question 4

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

Accepted Answer

Adding a catalyst.

Question 5

For the reaction $\mathrm{aA + bB \rightleftharpoons dD + eE}$, what is the equilibrium constant expression in terms of partial pressures ($K_p$)?

Accepted Answer

$K_p = \dfrac{(P_D)^d (P_E)^e}{(P_A)^a (P_B)^b}$

Question 6

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

Accepted Answer

Products predominate at equilibrium.

Question 7

Given $K_c = 0.212$ for $\mathrm{N_2O_4(g) \rightleftharpoons 2 NO_2(g)}$ at $100^\circ$C, what is $K_c$ for the reverse reaction $\mathrm{2 NO_2(g) \rightleftharpoons N_2O_4(g)}$?

Accepted Answer

$K_c = \dfrac{1}{0.212}$

Question 8

Which of the following is true for a heterogeneous equilibrium involving a pure solid?

Accepted Answer

The concentration of the solid is omitted from the equilibrium constant expression.

Question 9

For the decomposition of $\mathrm{CaCO_3(s) \rightleftharpoons CaO(s) + CO_2(g)}$, what is the equilibrium constant expression ($K_c$)?

Accepted Answer

$K_c = [CO_2]$

Question 10

A catalyst is added to a reaction at equilibrium. What effect does this have?

Accepted Answer

It increases the rate at which equilibrium is achieved, but does not change the equilibrium composition.

Question 11

If the reaction quotient $Q$ is less than the equilibrium constant $K$, what will happen?

Accepted Answer

The reaction will proceed toward the products.

Question 12

For the reaction $\mathrm{H_2(g) + I_2(g) \rightleftharpoons 2 HI(g)}$, if the initial concentrations are $[H_2] = 1.000\ \mathrm{mol/L}$, $[I_2] = 2.000\ \mathrm{mol/L}$, and $[HI] = 0$, and $K_c = 50.5$ at $448^\circ$C, what is the equilibrium concentration of $HI$?

Accepted Answer

$[HI] = 1.87\ \mathrm{mol/L}$

Question 13

Which of the following changes will increase the value of $K$ for an endothermic reaction?

Accepted Answer

Increasing the temperature.

Question 14

For the reaction $\mathrm{2 NOBr \rightleftharpoons 2 NO + Br_2}$, if $K_1 = 0.014$ and for $\mathrm{Br_2 + Cl_2 \rightleftharpoons 2 BrCl}$, $K_2 = 7.2$, what is the equilibrium constant for $\mathrm{2 NOBr + Cl_2 \rightleftharpoons 2 NO + 2 BrCl}$?

Accepted Answer

$K = 0.014 	imes 7.2$

Question 15

Which of the following is true about solubility and $K_{sp}$?

Accepted Answer

Solubility is the quantity of a substance that dissolves to form a saturated solution.

Question 16

For the reaction $\mathrm{Ba_3(PO_4)_2(s) \rightleftharpoons 3 Ba^{2+}(aq) + 2 PO_4^{3-}(aq)}$, what is the correct expression for the solubility-product constant ($K_{sp}$)?

Accepted Answer

$K_{sp} = [Ba^{2+}]^3 [PO_4^{3-}]^2$

Question 17

Which of the following is a correct application of Le Châtelier’s Principle?

Accepted Answer

Removing product will shift the equilibrium toward the products.

Question 18

If the stoichiometry of a reaction is doubled, how is the equilibrium constant affected?

Accepted Answer

It is squared.

Chemical Equilibrium: Principles, Calculations, and Applications

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