Question 1

For the reaction $2\ \mathrm{NO}_2(g) \rightleftharpoons \mathrm{N}_2\mathrm{O}_4(g)$ at 100\degree C, which of the following statements is TRUE at equilibrium?

Accepted Answer

The rate of the forward reaction equals the rate of the reverse reaction.

Question 2

Given the reaction $2\ \mathrm{SO}_2(g) + \mathrm{O}_2(g) \rightleftharpoons 2\ \mathrm{SO}_3(g)$ with $\Delta H^\circ = -198\ \mathrm{kJ}$, what will happen to the equilibrium position if the temperature is increased?

Accepted Answer

The equilibrium will shift to the left, producing more $\mathrm{SO}_2$ and $\mathrm{O}_2$.

Question 3

For the reaction $\mathrm{N}_2(g) + 3\ \mathrm{H}_2(g) ightleftharpoons 2\ \mathrm{NH}_3(g)$, $K = 3.7 	imes 10^8$ at 25\degree C. What does this value of $K$ imply about the position of equilibrium?

Accepted Answer

There are far more products than reactants at equilibrium.

Question 4

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

Accepted Answer

Adding a catalyst.

Question 5

For the reaction $2\ \mathrm{COF}_2 \rightleftharpoons \mathrm{CO}_2 + \mathrm{CF}_4$, if $[\mathrm{COF}_2]_{eq} = 0.255\ \mathrm{M}$, $[\mathrm{CF}_4]_{eq} = 0.118\ \mathrm{M}$, and $K_c = 2.00$ at $1000\degree C$, what is $[\mathrm{CO}_2]_{eq}$?

Accepted Answer

$0.118\ \mathrm{M}$

Question 6

For the reaction $2\ \mathrm{NO}_2(g) \rightleftharpoons \mathrm{N}_2\mathrm{O}_4(g)$, which of the following will cause the equilibrium to shift to the right?

Accepted Answer

Removing $\mathrm{N}_2\mathrm{O}_4$ from the system.

Question 7

For the reaction $\mathrm{I}_2(g) + \mathrm{Cl}_2(g) \rightleftharpoons 2\ \mathrm{ICl}(g)$ at 25\degree C, $K_p = 81.9$. If $P_{\mathrm{I}_2} = 0.114\ \mathrm{atm}$, $P_{\mathrm{Cl}_2} = 0.102\ \mathrm{atm}$, and $P_{\mathrm{ICl}} = 0.355\ \mathrm{atm}$, in which direction will the reaction proceed to reach equilibrium?

Accepted Answer

To the right (toward products)

Question 8

Which of the following is the correct equilibrium constant expression for the reaction $2\ \mathrm{N}_2\mathrm{O}_5 \rightleftharpoons 4\ \mathrm{NO}_2 + \mathrm{O}_2$?

Accepted Answer

$K = \dfrac{[\mathrm{NO}_2]^4 [\mathrm{O}_2]}{[\mathrm{N}_2\mathrm{O}_5]^2}$

Question 9

If the equilibrium constant $K$ for a reaction is much less than 1, which of the following is TRUE?

Accepted Answer

The reaction favors the formation of reactants.

Question 10

For the reaction $2\ \mathrm{A}(aq) + \mathrm{B}(aq) \rightleftharpoons 4\ \mathrm{C}(aq)$, if the initial concentrations are $[A]_0 = 1.00\ \mathrm{M}$, $[B]_0 = 1.00\ \mathrm{M}$, and $[C]_0 = 0$, and at equilibrium $[C] = 0.50\ \mathrm{M}$, what is $[A]$ at equilibrium?

Accepted Answer

$0.50\ \mathrm{M}$

Question 11

Which of the following is NOT included in the equilibrium constant expression for the reaction $\mathrm{CaCO}_3(s) \rightleftharpoons \mathrm{CaO}(s) + \mathrm{CO}_2(g)$?

Accepted Answer

$[\mathrm{CaCO}_3]$

Question 12

For the reaction $2\ \mathrm{NO}(g) + \mathrm{O}_2(g) ightleftharpoons 2\ \mathrm{NO}_2(g)$, $K_p = 2.2 	imes 10^{12}$ at 25\degree C. If $\Delta n = -1$, what is the relationship between $K_p$ and $K_c$?

Accepted Answer

$K_p = K_c (RT)^{-1}$

Question 13

A reaction mixture contains only products. What is the value of the reaction quotient $Q$, and in which direction will the reaction proceed?

Accepted Answer

$Q = \infty$, reaction proceeds to the left

Question 14

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

Accepted Answer

The new $K$ is the original $K$ squared.

Question 15

For the reaction $\mathrm{I}_2(g) ightleftharpoons 2\ \mathrm{I}(g)$, $K_c = 3.76 	imes 10^{-5}$ at $1000\ \mathrm{K}$. If $1.00$ mole of $\mathrm{I}_2$ is placed in a $2.00\ \mathrm{L}$ flask, what is the initial concentration of $\mathrm{I}_2$?

Accepted Answer

$0.50\ \mathrm{M}$

Question 16

Which of the following best describes the effect of a catalyst on a system at equilibrium?

Accepted Answer

It increases the rate at which equilibrium is achieved but does not affect the position of equilibrium.

Question 17

For the reaction $aA + bB \rightleftharpoons cC + dD$, the reaction quotient $Q$ is given by:

Accepted Answer

$Q = \dfrac{[C]^c [D]^d}{[A]^a [B]^b}$

Question 18

A system at equilibrium is disturbed by decreasing the volume of the container. For which reaction will the equilibrium shift to the right?

Accepted Answer

$2\ \mathrm{SO}_2(g) + \mathrm{O}_2(g) \rightleftharpoons 2\ \mathrm{SO}_3(g)$

Question 19

For the reaction $2\ \mathrm{CH}_4(g) \rightleftharpoons \mathrm{C}_2\mathrm{H}_2(g) + 3\ \mathrm{H}_2(g)$ at $1700\degree C$, if the initial $[\mathrm{CH}_4] = 0.115\ \mathrm{M}$ and the equilibrium $[\mathrm{C}_2\mathrm{H}_2] = 0.035\ \mathrm{M}$, what is the equilibrium concentration of $\mathrm{H}_2$?

Accepted Answer

$0.105\ \mathrm{M}$

Chemical Equilibrium: Principles, Calculations, and Le Châtelier’s Principle

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