Question 1

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

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

Which of the following processes is NOT reversible under normal conditions?

Accepted Answer

Frying an egg

Question 3

For the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2 NO_2$(g)}$$, which of the following is the correct equilibrium constant expression in terms of concentration?

Accepted Answer

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

Question 4

Which statement about chemical equilibrium is TRUE?

Accepted Answer

At equilibrium, the rates of the forward and reverse reactions are equal.

Question 5

Given the reaction $$\mathrm{N_2$(g) + 3 H_2$(g) \rightleftharpoons 2 NH_3$(g)}$$, what is the correct expression for the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = \dfrac{[NH_3$]^2}{[N_2$][H_2$]^3}$$

Question 6

Which of the following best explains why the equilibrium constant $$K_c is $$dimensionless for a balanced chemical equation?

Accepted Answer

Because the units cancel out due to the stoichiometry of the reaction.

Question 7

For the reaction $$\mathrm{aA + bB \rightleftharpoons cC + dD}$$, the equilibrium constant in terms of pressure $$K_p is $$related to $$K_c by $$which equation?

Accepted Answer

$$K_p = K_c (RT$$)^{(c+d)-(a+b)}$$

Question 8

A reaction is at equilibrium at 1000 K with $$K_c = 4.08 	imes 10$$^{-3}$$. If the reaction is 2$$ $$SO_2(g$$) + $$O_2(g$$) ightleftharpoons 2 $$SO_3(g$$)$$ and the total change in moles of gas is -1$, what is the value of K_p$? (Assume R = 0.0821$ L·atm·mol$$^{-1}$$·K$$^{-1}$$)

Accepted Answer

$$K_p = 0.335$$

Question 9

Which of the following is a correct statement about the reversibility of physical and chemical processes?

Accepted Answer

Some physical and chemical processes are reversible, while others are not.

Question 10

Which of the following best represents the law of mass action for the reaction $$\mathrm{aA + bB \rightleftharpoons cC + dD}$$?

Accepted Answer

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

Question 11

If the rate of the forward reaction is initially much greater than the rate of the reverse reaction, what happens as the system approaches equilibrium?

Accepted Answer

The rates of the forward and reverse reactions become equal.

Question 12

Which of the following is NOT a fact about a chemical system at equilibrium?

Accepted Answer

The reaction has stopped and no molecular changes occur.

Question 13

Which of the following real-life scenarios best illustrates a dynamic equilibrium?

Accepted Answer

A melting ice cube in a glass of water at 0°C

Question 14

Which of the following is the correct relationship between the equilibrium constant $$K_c$$ and the rate constants for the forward ($$k_f) $$and reverse ($$k_b) $$reactions for $$\mathrm{N_2O_4(g) \rightleftharpoons 2 NO_2$(g)}$$?

Accepted Answer

$$K_c = \dfrac{k_f}{k_b}$$

Question 15

Which of the following would NOT affect the value of the equilibrium constant $$K_c$$ for a given reaction?

Accepted Answer

Adding a catalyst

Chemical Equilibrium: Dynamic Nature, Law of Mass Action, and Equilibrium Constants

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