Question 1

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

Accepted Answer

The forward and reverse reactions continue at equal rates, so there is no net change in concentrations.

Question 2

For the reaction $$\mathrm{N_2O_4(g) \rightleftharpoons 2NO_2(g)}$$, which of the following is true at equilibrium?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 3

Given the equilibrium $$\mathrm{CO_2$(g) + H_2O(l) \rightleftharpoons H_2CO_3(aq)}$$, what will happen if more $$\mathrm{CO_2$} is $$added to the system at equilibrium?

Accepted Answer

The system will shift to produce more $$\mathrm{H_2CO_3}.$$

Question 4

For the reaction $$\mathrm{A + 2B \rightarrow 2C}$$, the equilibrium partial pressures are $$P_A = 1.20$$ atm, $$P_B = 1.40$$ atm, and $$P_C = 0.600$$ atm. What is the expression for $$K_p$$?

Accepted Answer

$$K_p = \dfrac{(P_C)^2$}{P_A (P_B)^2$}$$

Question 5

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

Accepted Answer

The mixture contains mostly products.

Question 6

Consider the reaction $$\mathrm{2NO(g) + O_2$(g) ightleftharpoons 2NO_2(g)}$$ with $$K_p = 4.2 	imes 10$$^{13}$$ at 300 K. What happens to K_p$ if the reaction is reversed?

Accepted Answer

$$K_p is $$inverted (reciprocal).

Question 7

A mixture of $$0.100$$ mol NO, $$0.050$$ mol H$$_2$$, and $$0.100$$ mol H$$_2O is $$placed in a $$1.00-L $$vessel for the reaction $$2NO(g) + 2H_2(g) \rightleftharpoons N_2$(g) + 2H_2O(g). At $$equilibrium, $$[NO] = 0.062 M. $$What is the equilibrium concentration of $$H_2$$?

Accepted Answer

$$0.012 M$$

Question 8

Which of the following changes will NOT shift the position of equilibrium for the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$?

Accepted Answer

Adding a catalyst

Question 9

For the dissolution of $$\mathrm{AgCl(s) ightleftharpoons Ag^+(aq) + Cl^-(aq)}$$ with $$K_{sp} = 1.8 	imes 10$$^{-10}$$, what is the molar solubility S$ in pure water?

Accepted Answer

$$1.3 	imes 10$$^{-5}$$ M

Question 10

If $$0.050 M$$ $$\mathrm{Cl^-} is $$added to a saturated solution of $$\mathrm{AgCl}$$, what is the new equilibrium concentration of $$\mathrm{Ag^+}$$?

Accepted Answer

$$3.6 	imes 10$$^{-9}$$ M

Question 11

Which of the following best explains why the addition of a common ion decreases the solubility of a salt?

Accepted Answer

It shifts the dissolution equilibrium to the left, decreasing ion concentrations.

Question 12

For the reaction $$\mathrm{A_2$ + 3B_2 \rightleftharpoons 2AB_3}$$, which of the following would increase the amount of $$\mathrm{AB_3$} at $$equilibrium?

Accepted Answer

Adding $$\mathrm{A_2$}$$

Question 13

A reaction mixture has $$Q \u003c K. $$What will happen as the system moves toward equilibrium?

Accepted Answer

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

Question 14

Which of the following is true for a reaction at equilibrium?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 15

For the reaction $$\mathrm{N_2$(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$$ ($$\Delta H = -92.4 kJ$$), what will happen if the temperature is increased?

Accepted Answer

The equilibrium will shift to the left, producing more $$\mathrm{N_2$}$$ and $$\mathrm{H_2$}.$$

Question 16

Which of the following is NOT included in the equilibrium constant expression for the reaction $$\mathrm{$$CaCO_3$$(s) \rightleftharpoons Ca$$^{2+}$$(aq) + CO_3$^{2-}(aq)}$$?

Accepted Answer

$$[$$CaCO_3$$]$$

Question 17

If the coefficients in a balanced chemical equation are doubled, how does the equilibrium constant change?

Accepted Answer

It is squared.

Question 18

A solution contains $$1.00 g of$$ $$\mathrm{$$MgF_2$$} ($$molar mass $$62.30 g/$$mol). If the molar solubility of $$\mathrm{$$MgF_2$$} is$$ $$1.31 	imes 10$$^{-3}$$ M, what is the minimum volume of water required to dissolve all the solid?

Accepted Answer

$$12.3 L$$

Question 19

Which of the following best describes the effect of adding an inert gas at constant volume to a system at equilibrium?

Accepted Answer

It increases the total pressure but does not shift the equilibrium.

Chemical Equilibrium: Principles, Expressions, and Applications

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