Question 1

For the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, which of the following is the correct equilibrium constant expression in terms of concentration ($$K_c$$)?

Accepted Answer

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

Question 2

Which statement best describes what happens when a chemical system reaches equilibrium?

Accepted Answer

The concentrations of reactants and products remain constant over time.

Question 3

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

Accepted Answer

$$K_p = \dfrac{P_{N_2O_4}}{(P_{NO_2$})^2$}$$

Question 4

In the Haber process, if the initial concentrations of $$\mathrm{N_2$}$$ and $$\mathrm{H_2$}$$ are doubled, what happens to the value of the equilibrium constant $$K_c$$?

Accepted Answer

It remains unchanged.

Question 5

Given the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$, how is the rate of disappearance of $$\mathrm{H_2$}$$ related to the rate of disappearance of $$\mathrm{N_2$}$$?

Accepted Answer

The rate of disappearance of $$\mathrm{H_2$} is $$three times that of $$\mathrm{N_2$}.$$

Question 6

Which of the following best explains why the same equilibrium mixture is produced regardless of the initial concentrations of reactants or products?

Accepted Answer

The equilibrium constant depends only on temperature, not on initial concentrations.

Question 7

For the reaction $$\mathrm{2SO_2(g) + O_2$(g) \rightleftharpoons 2SO_3(g)}$$, what is the value of $$\Delta n ($$change in moles of gas) used in the $$K_p$$ and $$K_c$$ relationship?

Accepted Answer

$$\Delta n = -1$$

Question 8

Which equation correctly relates $$K_p$$ and $$K_c$$ for a gaseous reaction?

Accepted Answer

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

Question 9

A reaction vessel contains $$\mathrm{N_2O_4}$$ and $$\mathrm{NO_2$} at $$equilibrium. If more $$\mathrm{NO_2$} is $$added, what will happen to the concentration of $$\mathrm{N_2O_4} as $$the system returns to equilibrium?

Accepted Answer

It will increase.

Question 10

For the reaction $$\mathrm{CO(g) + Cl_2$(g) ightleftharpoons $$COCl_2$$(g)}$$, if $$K_c = 1.2 	imes 10^4$ at 400 K, what does this indicate about the position of equilibrium?

Accepted Answer

The reaction favors the formation of $$\mathrm{$$COCl_2$$} at $$equilibrium.

Question 11

Which of the following is NOT included in the equilibrium constant expression for a heterogeneous equilibrium?

Accepted Answer

Pure solids and pure liquids.

Question 12

A student writes the equilibrium expression for $$\mathrm{$$CaCO_3$$(s) \rightleftharpoons CaO(s) + CO_2$(g)} as$$ $$K = \dfrac{[CaO][CO_2$]}{[$$CaCO_3$$]}. $$What is the error in this expression?

Accepted Answer

Concentrations of solids should not appear in the equilibrium expression.

Question 13

If the temperature of an exothermic reaction at equilibrium is increased, what happens to the value of the equilibrium constant $$K$$?

Accepted Answer

It decreases.

Question 14

For the reaction $$\mathrm{2NO_2(g) \rightleftharpoons N_2O_4(g)}$$, if the system is at equilibrium and the volume of the container is decreased, what will happen to the amount of $$\mathrm{N_2O_4}$$?

Accepted Answer

It will increase.

Question 15

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 coefficients, is constant.

Chemical Equilibrium: The Equilibrium Constant and Its Applications

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