Question 1

For the reaction $$aA + bB \rightleftharpoons cC + dD$$, which of the following is the correct equilibrium constant expression in terms of concentration?

Accepted Answer

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

Question 2

Consider the reaction $$2HI(g) \rightleftharpoons H_2$(g) + I_2$(g). $$Which of the following is the correct equilibrium constant expression in terms of partial pressures?

Accepted Answer

$$K_p = \frac{P_{H_2$} P_{I_2$}}{P_{HI}^2}$$

Question 3

Which of the following statements about the equilibrium constant $$K is $$TRUE?

Accepted Answer

The value of $$K$$ changes with temperature.

Question 4

For the reaction $$N_2O_4(g) \rightleftharpoons 2NO_2(g)$$, if the equilibrium constant $$K_p is $$much less than 1, which statement best describes the equilibrium mixture?

Accepted Answer

The mixture contains mostly $$N_2O_4.$$

Question 5

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

Accepted Answer

Pure solids

Question 6

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

Accepted Answer

$$\Delta n = -1$$

Question 7

If the equilibrium constant $$K$$ for a reaction is very large, what does this indicate about the position of equilibrium?

Accepted Answer

The reaction mixture contains mostly products at equilibrium.

Question 8

For the reaction $$aA + bB \rightleftharpoons cC + dD$$, how does increasing the temperature affect the equilibrium constant $$K$$ for an endothermic reaction?

Accepted Answer

The value of $$K$$ increases.

Question 9

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

Accepted Answer

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

Question 10

A mixture of $$A$$ and $$B is $$allowed to reach equilibrium according to $$A(g) \rightleftharpoons B(g). If $$the equilibrium constant $$K = 2$$ and the initial concentration of $$A is$$ $$1.0$$ mol/L and $$B is$$ $$0$$ mol/L, what is the equilibrium concentration of $$B$$?

Accepted Answer

$$0.67$$ mol/L

Question 11

For the reaction $$2NH_3(g) \rightleftharpoons N_2$(g) + 3H_2(g)$$, which of the following is the correct equilibrium constant expression in terms of partial pressures?

Accepted Answer

$$K_p = \frac{P_{N_2$} P_{H_2$}^3}{P_{NH_3$}^2}$$

Question 12

A student sets up a reaction at equilibrium and doubles the concentration of all reactants and products. What happens to the value of the equilibrium constant $$K$$?

Accepted Answer

It remains unchanged.

Question 13

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

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 14

For the reaction $$2NO_2(g) \rightleftharpoons N_2O_4(g)$$, what will happen to the equilibrium position if the pressure is increased?

Accepted Answer

The equilibrium will shift toward $$N_2O_4.$$

Question 15

Which of the following is a correct statement about $$K_c$$ and $$K_p$$ for a reaction where $$\Delta n = 0$$?

Accepted Answer

$$K_p = K_c$$

Question 16

A reaction has $$K_c = 1.5 	imes 10$$^{-5}$$ at 400$ K. What does this tell you about the equilibrium mixture?

Accepted Answer

Mostly reactants are present at equilibrium.

Question 17

For the reaction $$A(g) \rightleftharpoons B(g)$$, if the system is at equilibrium and more $$A is $$added, what will happen?

Accepted Answer

The concentration of $$B$$ will increase.

Question 18

Which of the following is the correct relationship between $$K_c$$ and $$K_p$$ for the reaction $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$ at temperature T$?

Accepted Answer

$$K_p = K_c(RT$$)^{-2}$$

Question 19

A reaction mixture at equilibrium contains $$[A] = 0.2 M$$, $$[B] = 0.3 M$$, $$[C] = 0.4 M$$, and $$[D] = 0.5 M $$for the reaction $$A + 2B \rightleftharpoons C + D. $$What is $$K_c$$?

Accepted Answer

$$K_c = \frac{[C][D]}{[A][B]^2} = \frac{0.4 	imes 0.5}{0.2 	imes (0.3)^2$} = 11.1$$

Chemical Equilibrium: Concepts, Constants, and Calculations

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