Question 1

Which of the following best describes dynamic equilibrium in a chemical reaction?

Accepted Answer

The rate of the forward reaction equals the rate of the reverse reaction, and concentrations of reactants and products remain constant.

Question 2

For the reaction $\mathrm{N_2(g) + O_2(g) \rightleftharpoons 2 NO(g)}$, the equilibrium constant $K$ is very small. What does this indicate about the composition of the equilibrium mixture?

Accepted Answer

The mixture contains mostly reactants.

Question 3

Given the reaction $\mathrm{2 CO(g) \rightleftharpoons CO_2(g) + C(s)}$, which of the following is the correct equilibrium constant expression?

Accepted Answer

$K = \dfrac{[CO_2]}{[CO]^2}$

Question 4

If the equilibrium constant $K$ for a reaction is much greater than 1, what can be concluded about the reaction at equilibrium?

Accepted Answer

Products predominate at equilibrium.

Question 5

For the gas-phase reaction $\mathrm{N_2(g) + 3 H_2(g) \rightleftharpoons 2 NH_3(g)}$, how will the equilibrium shift if the pressure is increased by decreasing the volume?

Accepted Answer

The equilibrium will shift toward the side with fewer moles of gas.

Question 6

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 7

For the reaction $\mathrm{A(g) + 2 B(g) \rightleftharpoons 3 C(g)}$, the equilibrium constant in terms of concentration is $K_c$. What is the relationship between $K_p$ and $K_c$?

Accepted Answer

$K_p = K_c (RT)^{2}$

Question 8

A reaction mixture initially contains only reactants. As the reaction proceeds toward equilibrium, what happens to the value of the reaction quotient $Q$?

Accepted Answer

$Q$ increases until it equals $K$.

Question 9

If the reaction $\mathrm{2 SO_2(g) + O_2(g) \rightleftharpoons 2 SO_3(g)}$ is exothermic, what will happen to the equilibrium position if the temperature is increased?

Accepted Answer

The equilibrium will shift to the left, forming more $SO_2$ and $O_2$.

Question 10

For the reaction $\mathrm{H_2(g) + I_2(g) \rightleftharpoons 2 HI(g)}$, if the initial concentrations of $H_2$ and $I_2$ are both 0.050 M and $K = 59.3$ at 400°C, what is the equilibrium concentration of $HI$?

Accepted Answer

0.080 M

Question 11

Which of the following actions will shift the equilibrium to the right for the reaction $\mathrm{CaCO_3(s) \rightleftharpoons CaO(s) + CO_2(g)}$?

Accepted Answer

Removing $CO_2$

Question 12

If the equilibrium constant for a reaction is $K$, what is the equilibrium constant for the reverse reaction?

Accepted Answer

$1/K$

Question 13

A mixture at equilibrium contains $[PCl_3] = 0.202$ atm, $[Cl_2] = 0.256$ atm, and $[PCl_5] = 3.45$ atm for the reaction $\mathrm{PCl_3(g) + Cl_2(g) \rightleftharpoons PCl_5(g)}$. What is the value of $K_p$?

Accepted Answer

0.178

Question 14

For the reaction $\mathrm{SO_2Cl_2(g) \rightleftharpoons SO_2(g) + Cl_2(g)}$ at 100°C, $K_c = 0.078$. If $[SO_2Cl_2] = 0.108$ M, $[SO_2] = 0.052$ M, and $[Cl_2] = 0.052$ M, what is the value of $Q$ and which direction will the reaction proceed?

Accepted Answer

$Q = 0.025$, reaction will shift right.

Question 15

If the stoichiometric coefficients in a balanced chemical equation are doubled, how does the equilibrium constant change?

Accepted Answer

It is squared.

Question 16

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

Accepted Answer

Their activities are defined as 1 and do not affect the equilibrium expression.

Question 17

A catalyst is added to a reaction mixture at equilibrium. What is the effect on the equilibrium concentrations of reactants and products?

Accepted Answer

There is no change in equilibrium concentrations.

Question 18

For the reaction $\mathrm{A(g) \rightleftharpoons 2 B(g)}$ with $K_c = 0.33$, if the initial concentration of $A$ is 1.0 M and $B$ is 0 M, what is the equilibrium concentration of $B$ (rounded to two decimal places)?

Accepted Answer

0.72 M

Question 19

Which of the following statements about the reaction quotient $Q$ is correct?

Accepted Answer

$Q$ can be used to predict the direction in which a reaction will proceed to reach equilibrium.

Chapter 15: Chemical Equilibrium – Mini-Textbook Study Guide

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