Q: For the reaction $$\mathrm{CO}_2 \rightleftharpoons \mathrm{CO} + \mathrm{O}_2 at 1000$$°C and total pressure of 20.0 atm, if $$\mathrm{CO}_2$$ makes up 12.5 mol out of 20.0 mol total, what is the partial pressure of $$\mathrm{CO}_2$$?

$$P_{\mathrm{CO}_2$$} = \frac{12.5}{20.0} \times 20.0 = 12.5$$ atm

Question 1

For the equilibrium reaction $$\mathrm{AgI}_s + \mathrm{H}_2O \rightleftharpoons \mathrm{OH}^- + \mathrm{HI}$$, which of the following correctly expresses the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = [\mathrm{OH}^-][\mathrm{HI}]$$

Question 2

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

Accepted Answer

The products are favored at equilibrium.

Question 3

Given the reaction $$\mathrm{CH}_3\mathrm{COOH} + \mathrm{C}_2\mathrm{H}_5\mathrm{OH} \rightleftharpoons \mathrm{CH}_3\mathrm{COOC}_2\mathrm{H}_5 + \mathrm{H}_2O$$, and initial concentrations of 1.00 mol each of acetic acid and ethanol, with $$K_c = 4.0$$, how many moles of ethyl acetate will be produced at equilibrium?

Accepted Answer

1.33 mol

Question 4

For the equilibrium $$2\mathrm{NO}_2 \rightleftharpoons 2\mathrm{NO} + \mathrm{O}_2$$, if the equilibrium concentrations are $$[\mathrm{NO}_2] = 0.0200 M$$, $$[\mathrm{NO}] = 0.0300 M$$, and $$[\mathrm{O}_2] = 0.0100 M$$, what is the value of $$K_c$$?

Accepted Answer

$$K_c = \frac{[\mathrm{NO}]^2[\mathrm{O}_2]}{[\mathrm{NO}_2]^2} = \frac{(0.0300)^2$ 	imes 0.0100}{(0.0200)^2$} = 0.225$$

Question 5

When the pressure of a system at equilibrium is increased by decreasing the volume, what happens to the equilibrium position for the reaction $$2\mathrm{NO}_2 \rightleftharpoons 2\mathrm{NO} + \mathrm{O}_2$$?

Accepted Answer

The equilibrium shifts toward the side with fewer gas molecules.

Question 6

For the reaction $$\mathrm{CO}_2 \rightleftharpoons \mathrm{CO} + \mathrm{O}_2 at 1000$$°C and total pressure of 20.0 atm, if $$\mathrm{CO}_2$$ makes up 12.5 mol out of 20.0 mol total, what is the partial pressure of $$\mathrm{CO}_2$$?

Accepted Answer

$$P_{\mathrm{CO}_2$$} = \frac{12.5}{20.0} 	imes 20.0 = 12.5$$ atm

Question 7

Which of the following statements about the effect of a catalyst on a chemical equilibrium is correct?

Accepted Answer

A catalyst speeds up the attainment of equilibrium but does not change the equilibrium constant.

Question 8

For the reaction $$\mathrm{N}_2 + 3\mathrm{H}_2 \rightleftharpoons 2\mathrm{NH}_3$$, what is the effect of increasing the temperature on the equilibrium if the reaction is exothermic?

Accepted Answer

The equilibrium shifts toward the reactants.

Question 9

Given the equilibrium $$\mathrm{NO}_2 \rightleftharpoons \mathrm{NO} + \frac{1}{2}\mathrm{O}_2$$, and the equilibrium constant $$K_p is $$defined as $$K_p = \frac{P_{\mathrm{NO}} P$$_{\mathrm{O}$$_2}^{1/2}}{P$$_{\mathrm{NO}$$_2}}$$, what is the relationship between $$K_p$$ and $$K_c$$?

Accepted Answer

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

Question 10

If the equilibrium constant $$K_c$$ for a reaction is 0.01, what does this indicate about the concentrations of reactants and products at equilibrium?

Accepted Answer

Reactants are favored at equilibrium.

Question 11

For the reaction $$\mathrm{N}_2\mathrm{O}_4 \rightleftharpoons 2\mathrm{NO}_2$$, if the partial pressure of $$\mathrm{NO}_2 is 0.40 $$atm and $$\mathrm{N}_2\mathrm{O}_4 is 0.20 $$atm, what is the value of $$K_p$$?

Accepted Answer

$$K_p = \frac{(0.40)^2$}{0.20} = 0.80$$

Question 12

Which of the following best describes the effect of increasing pressure on a reaction where the number of gas molecules decreases?

Accepted Answer

The equilibrium shifts toward the side with fewer gas molecules.

Question 13

For the reaction $$\mathrm{CO}_2 \rightleftharpoons \mathrm{CO} + \mathrm{O}_2$$, if the total pressure is 20.0 atm and the partial pressure of $$\mathrm{CO}_2 is 12.5 $$atm, what is the mole fraction of $$\mathrm{CO}_2$$?

Accepted Answer

$$\frac{12.5}{20.0} = 0.625$$

Question 14

Which equation relates the change in standard free energy $$\Delta G^\circ to $$the equilibrium constant $$K$$?

Accepted Answer

$$\Delta G^\circ = -RT \ln K$$

Question 15

For the reaction $$\mathrm{N}_2 + 3\mathrm{H}_2 \rightleftharpoons 2\mathrm{NH}_3$$, what happens to the equilibrium constant $$K if $$the temperature is increased for an exothermic reaction?

Accepted Answer

The equilibrium constant decreases.

Question 16

Which of the following is true about the effect of temperature on equilibrium for an endothermic reaction?

Accepted Answer

Increasing temperature shifts equilibrium toward the products.

Question 17

For the equilibrium $$\mathrm{N}_2 + 3\mathrm{H}_2 \rightleftharpoons 2\mathrm{NH}_3$$, what is the effect of adding a catalyst?

Accepted Answer

The rate of reaching equilibrium increases, but the equilibrium position does not change.

Question 18

Which of the following best describes Le Chatelier's Principle?

Accepted Answer

A system at equilibrium will shift to counteract a change in conditions.

Chemical Equilibrium: Principles, Calculations, and Applications

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