Question 1

Which of the following best describes the state of chemical equilibrium for the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)} as $$shown in the first image?

Accepted Answer

The rates of the forward and reverse reactions are equal, and the concentrations of $$\mathrm{NO_2$}$$ and $$\mathrm{N_2O_4}$$ remain constant over time.

Question 2

Refer to the second image. What does the point where the two curves meet represent?

Accepted Answer

The time when the rates of the forward and reverse reactions are equal, indicating equilibrium.

Question 3

Given the equation $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$, which of the following is the correct equilibrium constant expression ($$K_c$$)?

Accepted Answer

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

Question 4

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

Accepted Answer

The reaction mixture contains mostly products.

Question 5

For the reaction $$\mathrm{CH_4$(g) + 2H_2S(g) \rightleftharpoons CS_2$(g) + 4H_2(g)}$$, write the equilibrium constant expression $$K_c.$$

Accepted Answer

$$K_c = \dfrac{[CS_2$][H_2$]^4}{[CH_4$][H_2S]^2}$$

Question 6

Which of the following changes will increase the value of the equilibrium constant $$K_c$$ for an endothermic reaction?

Accepted Answer

Increasing the temperature.

Question 7

If the volume of a reaction vessel containing only gases is decreased, what will happen to the equilibrium position of the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$?

Accepted Answer

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

Question 8

Which of the following statements about catalysts and equilibrium is correct?

Accepted Answer

A catalyst speeds up both the forward and reverse reactions equally, but does not change the equilibrium constant.

Question 9

For the reaction $$\mathrm{2NO(g) + O_2$(g) \rightleftharpoons 2NO_2(g)}$$, which of the following is the correct $$K_c$$ expression?

Accepted Answer

$$K_c = \dfrac{[NO_2$]^2}{[NO]^2[O_2$]}$$

Question 10

A mixture initially contains 1.0 M $$\mathrm{N_2O_4}$$ and 0 M $$\mathrm{NO_2$}. At $$equilibrium, $$\mathrm{[N_2O_4]} = 0.7 M. $$What is $$\mathrm{[NO_2$]} at $$equilibrium for $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$?

Accepted Answer

0.6 M

Question 11

If $$Q_c \u003c K_c$$ for a reaction mixture, what will happen as the system moves toward equilibrium?

Accepted Answer

The reaction will shift to the right, forming more products.

Question 12

For the reaction $$\mathrm{$$PCl_5$$(g) ightleftharpoons $$PCl_3$$(g) + Cl_2$(g)}$$ with $$K_c = 5.8 	imes 10$$^{-2}$$, what does the small value of K_c$ indicate?

Accepted Answer

The reaction mixture contains mostly reactants at equilibrium.

Question 13

Which of the following is omitted from equilibrium constant expressions?

Accepted Answer

Pure solids and pure liquids

Question 14

If the equilibrium constant for a reaction is $$K_c = 1.0 	imes 10$$^{-10}$$, which statement is true?

Accepted Answer

The reaction hardly proceeds at all; mostly reactants are present at equilibrium.

Question 15

For the reaction $$\mathrm{cis	ext{-}stilbene ightleftharpoons trans	ext{-}stilbene}$$, if you start with 0.850 M cis-stilbene and $$K_c = 24.0$$, what is the equilibrium concentration of trans-stilbene?

Accepted Answer

0.816 M

Question 16

Which of the following will NOT change the value of the equilibrium constant $$K_c$$ for a given reaction?

Accepted Answer

Adding a catalyst.

Question 17

For the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, what will happen if $$\mathrm{N_2$} is $$added to the system at equilibrium?

Accepted Answer

The reaction will shift to the right, forming more $$\mathrm{NH_3$}.$$

Question 18

Which of the following is the correct relationship between $$K_p$$ and $$K_c$$ for a reaction involving gases?

Accepted Answer

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

Question 19

If the reaction $$\mathrm{A(g) \rightleftharpoons 2B(g)} is at $$equilibrium and the volume of the container is doubled, what will happen to the equilibrium position?

Accepted Answer

It will shift to the right, forming more B.

Chemical Equilibrium: Principles, Constants, and Applications

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