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, and the concentrations of reactants and products remain constant.

Question 2

Which of the following processes is an example of a reversible physical change?

Accepted Answer

Melting of ice to water.

Question 3

Given the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2 NO_2$(g)}$$, 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

Which statement about chemical equilibrium is FALSE?

Accepted Answer

At equilibrium, the reaction has stopped.

Question 5

For 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 cooking an egg is not a reversible process?

Accepted Answer

The process involves a chemical change that cannot be undone under normal conditions.

Question 7

If the rate of the forward reaction is given by $$	ext{Rate}_f = k_f [N_2O_4]$$ and the rate of the reverse reaction is $$	ext{Rate}_b = k_b [NO_2$]^2$$, what condition must be met at equilibrium?

Accepted Answer

$$k_f [N_2O_4] = k_b [NO_2$]^2$$

Question 8

Which of the following is the correct relationship between $$K_c$$ and $$K_p$$ for the reaction $$aA + bB \rightleftharpoons cC + dD$$ involving gases?

Accepted Answer

$$K_p = K_c (RT$$)^{\Delta n}$$, where $$\Delta n = (c + d) - (a + b)$$

Question 9

A reaction is at equilibrium at 1000 K with $$K_c = 4.08 	imes 10$$^{-3}$$. If $$\Delta n = 1$$ and R = 0.0821$$ \ \mathrm{L \cdot atm \cdot $$mol^{-1}$$ \cdot $$K^{-1}$$}$$, what is the value of K_p$?

Accepted Answer

$$K_p = 0.335$$

Question 10

Which of the following statements about the equilibrium constant $$K_c is $$correct?

Accepted Answer

$$K_c is $$constant for a given reaction at a specific temperature.

Question 11

Which of the following best describes the law of mass action?

Accepted Answer

At equilibrium, the ratio of the concentrations of products to reactants, each raised to the power of their stoichiometric coefficients, is constant.

Question 12

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

Accepted Answer

Adding a catalyst.

Question 13

For the reaction $$2 SO_2$(g) + O_2$(g) \rightleftharpoons 2 SO_3$(g)$$, which of the following is the correct $$K_c$$ expression?

Accepted Answer

$$K_c = \dfrac{[SO_3$]^2}{[SO_2$]^2 [O_2$]}$$

Question 14

Which of the following is a correct statement about reversible and irreversible processes?

Accepted Answer

Some physical changes, such as melting and freezing, are reversible.

Question 15

A student claims that at equilibrium, the concentrations of reactants and products must be equal. Is this correct? Why or why not?

Accepted Answer

No, because equilibrium means the rates of forward and reverse reactions are equal, not the concentrations.

Question 16

Which of the following best illustrates the concept of dynamic equilibrium using a real-world analogy?

Accepted Answer

A bridge with cars moving at the same rate in both directions, so the number of cars on the bridge stays constant.

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

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