Q: For the reaction $$2\text{NO}_2(g) \rightleftharpoons \text{N}_2\text{O}_4(g)$$, which of the following expressions correctly represents the equilibrium constant $$K_c$$?

$$K_c = \dfrac{[\text{N}_2\text{O}_4]}{[\text{NO}_2]^2}$$

Q: Which of the following changes will shift the equilibrium of the reaction $$\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) to $$the right, according to Le Châtelier’s Principle?

Increasing the concentration of $$\text{N}_2$$

Q: Which of the following is the correct net ionic equation for the reaction between hydrochloric acid and sodium hydroxide?

$$\text{H}^+(aq) + \text{OH}^-(aq) \rightarrow \text{H}_2\text{O}(l)$$

Q: Which of the following acids is the strongest, based on the given $$K_a$$ values?

Chlorous acid, $$K_a = 1.0 \times 10$$^{-2}$$

Q: Which of the following is a conjugate acid-base pair?

$$\text{NH}_4^+$$ and $$\text{NH}_3$$

Question 1

Which of the following best describes chemical equilibrium in a closed system?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 2

For the reaction $$2	ext{NO}_2(g) ightleftharpoons 	ext{N}_2	ext{O}_4(g)$$, which of the following expressions correctly represents the equilibrium constant $$K_c$$?

Accepted Answer

$$K_c = \dfrac{[	ext{N}_2	ext{O}_4]}{[	ext{NO}_2]^2}$$

Question 3

A reaction mixture initially contains only reactants. As the reaction proceeds, the rate of the forward reaction decreases and the rate of the reverse reaction increases. What happens when equilibrium is reached?

Accepted Answer

The rates of the forward and reverse reactions become equal.

Question 4

Given the reaction $$2	ext{H}_2	ext{S}(g) + 	ext{CH}_4(g) ightleftharpoons 	ext{CS}_2(g) + 4	ext{H}_2(g)$$ with $$K_c = 3.4 	imes 10$$^{-4}$$, if Q_c$$ \u003e K_c$$, in which direction will the reaction proceed?

Accepted Answer

Toward the reactants (left)

Question 5

Which of the following changes will shift the equilibrium of the reaction $$	ext{N}_2(g) + 3	ext{H}_2(g) ightleftharpoons 2	ext{NH}_3(g) to $$the right, according to Le Châtelier’s Principle?

Accepted Answer

Increasing the concentration of $$	ext{N}_2$$

Question 6

Which of the following is the correct net ionic equation for the reaction between hydrochloric acid and sodium hydroxide?

Accepted Answer

$$	ext{H}^+(aq) + 	ext{OH}^-(aq) ightarrow 	ext{H}_2	ext{O}(l)$$

Question 7

Which of the following statements about acids and bases is correct according to the Brønsted-Lowry definition?

Accepted Answer

An acid is a substance that donates a proton.

Question 8

A solution has a pH of 3. Which of the following best describes the solution?

Accepted Answer

Strongly acidic

Question 9

Which of the following acids is the strongest, based on the given $$K_a$$ values?

Accepted Answer

Chlorous acid, $$K_a = 1.0 	imes 10$$^{-2}$$

Question 10

What is the pH of a solution with $$[	ext{H}_3	ext{O}^+] = 1.0 	imes 10$$^{-4}$$\ 	ext{M}$$?

Accepted Answer

pH = 4

Question 11

During a titration of a weak acid with a strong base, which of the following is true at the equivalence point?

Accepted Answer

The pH is greater than 7.

Question 12

Which of the following best explains why the addition of a catalyst does not affect the position of equilibrium?

Accepted Answer

A catalyst increases the rate of both the forward and reverse reactions equally.

Question 13

If the $$K_w$$ for water at 25°C is $$1.0 	imes 10$$^{-14}$$, what is the pOH of a neutral solution at this temperature?

Accepted Answer

pOH = 7

Question 14

Which of the following is a conjugate acid-base pair?

Accepted Answer

$$	ext{NH}_4^+$$ and $$	ext{NH}_3$$

Question 15

A buffer solution is prepared by mixing acetic acid and sodium acetate. Which of the following best describes the function of this buffer?

Accepted Answer

It maintains a constant pH by neutralizing added acids or bases.

Question 16

Which indicator would be most appropriate for a titration between a strong acid and a strong base?

Accepted Answer

An indicator with a transition range around pH 7

Question 17

Which of the following best describes the effect of decreasing the volume of a container on the equilibrium of the reaction $$2	ext{SO}_2(g) + 	ext{O}_2(g) ightleftharpoons 2	ext{SO}_3(g)$$?

Accepted Answer

The equilibrium shifts toward the side with fewer moles of gas.

Question 18

Which of the following is the correct relationship between $$K_a$$, $$K_b$$, and $$K_w$$ for a conjugate acid-base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 19

A sample of seawater has a pH of 8. What is the $$[	ext{H}_3	ext{O}^+]$$ concentration?

Accepted Answer

$$1.0 	imes 10$$^{-8}$$\ 	ext{M}$$

Unit 8: Chemical Equilibrium, Acids, and Bases – Study Notes

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