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

$$\mathrm{H_2O}$$ \text{ and } \mathrm{OH^-}$

Q: A solution has a pH of 3.5. What is the concentration of hydronium ions $$[\mathrm{H_3O^+}] in $$this solution?

$$3.2 \times 10$$^{-4}$$~\mathrm{M}$$

Question 1

Which of the following statements best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

A catalyst lowers the activation energy, allowing equilibrium to be reached faster without changing the equilibrium composition.

Question 2

According to the Brønsted–Lowry definition, which of the following is an acid-base reaction?

Accepted Answer

$$\mathrm{NH_3$ (aq) + H_2O (l) \rightarrow NH_4$^+ (aq) + OH^- (aq)}$$

Question 3

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

Accepted Answer

$$\mathrm{H_2O}$$ 	ext{ and } \mathrm{OH^-}$

Question 4

A solution has a pH of 3.5. What is the concentration of hydronium ions $$[\mathrm{H_3O^+}] in $$this solution?

Accepted Answer

$$3.2 	imes 10$$^{-4}$$~\mathrm{M}$$

Question 5

Which of the following acids is considered a strong acid in aqueous solution?

Accepted Answer

Hydrochloric acid ($$\mathrm{HCl})$$

Question 6

Calculate the pH of a $$0.020~\mathrm{M}$$ solution of $$\mathrm{$$HNO_3$$} (a $$strong acid).

Accepted Answer

1.70

Question 7

Which of the following statements about the autoionization of water is correct?

Accepted Answer

The process produces equal concentrations of $$\mathrm{H_3O^+}$$ and $$\mathrm{OH^-} in $$pure water.

Question 8

A $$0.10~\mathrm{M}$$ solution of benzoic acid ($$\mathrm{C_6H_5COOH}) $$has a pH of 2.60. What is the percent ionization of benzoic acid in this solution?

Accepted Answer

2.5\%

Question 9

Which of the following best explains why strong acids have weak conjugate bases?

Accepted Answer

Strong acids completely dissociate, leaving their conjugate bases with little tendency to accept protons.

Question 10

A $$0.0033~\mathrm{M}$$ solution of $$\mathrm{Sr(OH)_2} is $$prepared. What is the $$[\mathrm{OH^-}] in $$this solution?

Accepted Answer

$$0.0066~\mathrm{M}$$

Question 11

Which of the following solutions will have the lowest pH?

Accepted Answer

$$0.10~\mathrm{M}$$~\mathrm{HCl}$

Question 12

A $$0.010~\mathrm{M}$$ solution of benzoic acid ($$\mathrm{C_6H_5COOH}) $$has a pH of 3.11. What is the percent ionization?

Accepted Answer

7.7\%

Question 13

Which of the following is true for an aqueous solution at 25$$^\circC $$with $$[\mathrm{H_3O^+}] = 1.0 	imes 10$$^{-7}$$~\mathrm{M}$$?

Accepted Answer

The solution is neutral.

Question 14

Which of the following indicators would be most suitable for detecting the endpoint of a titration between a strong acid and a strong base?

Accepted Answer

Phenolphthalein (range 8.3–10.0)

Question 15

A $$5.0~\mathrm{L}$$ solution contains $$2.00~\mathrm{g} of$$ $$\mathrm{Ca(OH)_2}$$ ($$\mathrm{MW} = 74.09~\mathrm{g/mol}). $$What is the pH of the solution?

Accepted Answer

12.03

Question 16

Which of the following best describes an amphiprotic species?

Accepted Answer

A molecule that can act as both a proton donor and a proton acceptor.

Question 17

If the $$K_a$$ for a weak acid is $$1.5 	imes 10$$^{-5}$$ and the initial concentration is 0.010$$~\mathrm{M}$$, what is the approximate $$[\mathrm{H_3O^+}]$$ at equilibrium?

Accepted Answer

$$3.9 	imes 10$$^{-4}$$~\mathrm{M}$$

Question 18

Which of the following best explains why the percent ionization of a weak acid decreases as its concentration increases?

Accepted Answer

The equilibrium shifts to favor the undissociated acid as concentration increases.

Question 19

A window cleaning solution contains $$[\mathrm{OH^-}] = 1.87 	imes 10$$^{-6}$$~\mathrm{M}. $$What is the pH of the solution?

Accepted Answer

8.27

Acid–Base Equilibria and Acid–Base Strength in Aqueous Solutions

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