Q: For the reaction $$2\text{Cu}^{2+}(aq) + \text{Sn}^{2+}(aq) \rightleftharpoons 2\text{Cu}^{+}(aq) + \text{Sn}^{4+}(aq)$$, what is the correct equilibrium constant expression?

$$K = \frac{[\text{Cu}^{+}]^2[\text{Sn}^{4+}]}{[\text{Cu}^{2+}]^2[\text{Sn}^{2+}]}$$

Q: For the reaction $$\text{CaCO}_3(s) \rightleftharpoons \text{CaO}(s) + \text{CO}_2(g)$$, what is the equilibrium constant expression?

$$K = \frac{P$$_{\text{CO}$$_2}}{P^\circ}$$

Q: For the gas-phase reaction $$2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g)$$, if the equilibrium constant $$K_c is$$ $$2.8 × 10^2 at 1000 K$$, what is the value of $$K_P at $$this temperature? (Assume $$R = 0.08314 L$$·bar·K$$^{-1}$$·mol$$^{-1})$$

$$K_P = K_c \times (RT$$)^{-1}$$

Question 1

Which statement best describes the dynamic nature of chemical equilibrium?

Accepted Answer

At equilibrium, the forward and reverse reactions occur at the same rate, so the concentrations remain constant.

Question 2

For the reaction $$2	ext{Cu}^{2+}(aq) + 	ext{Sn}^{2+}(aq) ightleftharpoons 2	ext{Cu}^{+}(aq) + 	ext{Sn}^{4+}(aq)$$, what is the correct equilibrium constant expression?

Accepted Answer

$$K = \frac{[	ext{Cu}^{+}]^2[	ext{Sn}^{4+}]}{[	ext{Cu}^{2+}]^2[	ext{Sn}^{2+}]}$$

Question 3

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

Accepted Answer

The concentration of a pure solid

Question 4

For the reaction $$	ext{CaCO}_3(s) ightleftharpoons 	ext{CaO}(s) + 	ext{CO}_2(g)$$, what is the equilibrium constant expression?

Accepted Answer

$$K = \frac{P$$_{	ext{CO}$$_2}}{P^\circ}$$

Question 5

If the equilibrium constant $$K$$ for a reaction is very large ($$K \gg 1$$), what does this indicate about the reaction?

Accepted Answer

The reaction favors the formation of products.

Question 6

For the gas-phase reaction $$2	ext{SO}_2(g) + 	ext{O}_2(g) ightleftharpoons 2	ext{SO}_3(g)$$, if the equilibrium constant $$K_c is$$ $$2.8 × 10^2 at 1000 K$$, what is the value of $$K_P at $$this temperature? (Assume $$R = 0.08314 L$$·bar·K$$^{-1}$$·mol$$^{-1})$$

Accepted Answer

$$K_P = K_c 	imes (RT$$)^{-1}$$

Question 7

If $$Q \u003c K$$ for a reaction mixture, what will happen to the system?

Accepted Answer

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

Question 8

Which of the following changes will NOT affect the equilibrium position of a reaction?

Accepted Answer

Adding a catalyst

Question 9

For the reaction $$	ext{N}_2(g) + 3	ext{H}_2(g) ightleftharpoons 2	ext{NH}_3(g)$$, what will happen if the volume of the container is decreased?

Accepted Answer

The equilibrium will shift toward the side with fewer moles of gas (toward NH$$_3).$$

Question 10

Which statement about the effect of temperature on equilibrium is correct?

Accepted Answer

Increasing temperature favors the endothermic direction of the reaction.

Question 11

For the reaction $$	ext{AgI}(s) ightleftharpoons 	ext{Ag}^+(aq) + 	ext{I}^-(aq)$$, what is the activity of AgI(s) in the equilibrium constant expression?

Accepted Answer

$$a_{	ext{AgI}} = 1$$

Question 12

If the equilibrium constant for a reaction is $$K = 10$$^{-10}$$, what does this indicate about the reaction?

Accepted Answer

The reaction hardly occurs; reactants are favored.

Question 13

What is the effect of adding an inert gas to a constant-volume equilibrium mixture?

Accepted Answer

It does not affect the equilibrium position.

Question 14

For the reaction $$2	ext{SO}_2(g) + 	ext{O}_2(g) ightleftharpoons 2	ext{SO}_3(g)$$, what happens to the equilibrium if the temperature is increased?

Accepted Answer

The equilibrium shifts toward the reactants (SO$$_2$$ and O$$_2).$$

Question 15

If the coefficients in a balanced chemical equation are doubled, what happens to the equilibrium constant?

Accepted Answer

The equilibrium constant is squared.

Question 16

A reaction mixture contains only reactants initially. What is the value of $$Q$$ and which direction will the reaction proceed?

Accepted Answer

$$Q = 0$$, reaction proceeds to the right (toward products).

Question 17

For the reaction $$	ext{NH}_4	ext{HS}(s) ightleftharpoons 	ext{NH}_3(g) + 	ext{H}_2	ext{S}(g)$$, if $$K_P = 0.108 at 25$$°C, what is the total pressure at equilibrium?

Accepted Answer

$$P_{	ext{total}} = 2 	imes \sqrt{K_P}$$

Question 18

Which of the following best describes Le Châtelier’s Principle?

Accepted Answer

A system at equilibrium responds to a disturbance by shifting in a direction that partially offsets the disturbance.

Principles of Chemical Equilibrium: Structured Study Notes

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