$$pH = -\log(2.5 \times 10$$^{-5}$$) = 4.60$$

$$K_a = \dfrac{[H^+][HCOO^-]}{[HCOOH]} = \dfrac{(4.2 \times 10$$^{-3}$$)^2$$}{0.10} = 1.8 \times $$10^{-5}$

Question 1

Which of the following statements best describes the difference between the Arrhenius and Brønsted–Lowry definitions of acids and bases?

Accepted Answer

Arrhenius acids increase hydrogen ion concentration in water, while Brønsted–Lowry acids are proton donors.

Question 2

Water is described as amphiprotic. What does this mean?

Accepted Answer

Water can act as both a proton donor and a proton acceptor.

Question 3

Which of the following pairs is a conjugate acid–base pair?

Accepted Answer

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

Question 4

Which of the following statements about strong acids is correct?

Accepted Answer

Strong acids have weak conjugate bases.

Question 5

At $$25^\circ\mathrm{C}$$, the ion product constant for water is $$K_w = 1.0 	imes 10$$^{-14}$$. What is the pH of pure water at this temperature?

Accepted Answer

$$7.00$$

Question 6

A solution has $$[\mathrm{H^+}] = 2.5 	imes 10$$^{-5}$$\ \mathrm{M}. $$What is the pH of this solution?

Accepted Answer

$$pH = -\log(2.5 	imes 10$$^{-5}$$) = 4.60$$

Question 7

Which of the following best explains why $$\mathrm{$$HClO_4$$} is a $$stronger acid than $$\mathrm{$$HClO_2$$}$$?

Accepted Answer

Perchloric acid has more oxygen atoms, increasing the oxidation state of chlorine and stabilizing the conjugate base.

Question 8

Calculate the $$K_a$$ for formic acid if a $$0.10\ \mathrm{M}$$ solution has a pH of $$2.38.$$

Accepted Answer

$$K_a = \dfrac{[H^+][HCOO^-]}{[HCOOH]} = \dfrac{(4.2 	imes 10$$^{-3}$$)^2$$}{0.10} = 1.8 	imes $$10^{-5}$

Question 9

Which of the following salts will produce a basic solution when dissolved in water?

Accepted Answer

$$\mathrm{NaCH_3COO}$$

Question 10

Which of the following factors increases the strength of a binary acid HX as you move down a group in the periodic table?

Accepted Answer

Decreasing bond strength

Question 11

A $$0.15\ \mathrm{M}$$ solution of ammonia ($$NH_3) $$has $$K_b = 1.8 	imes 10$$^{-5}$$. What is the pH of the solution?

Accepted Answer

$$pH = 11.20$$

Question 12

Which of the following is a Lewis acid but not a Brønsted–Lowry acid?

Accepted Answer

$$\mathrm{BF_3$}$$

Question 13

Which of the following best describes the relationship between $$K_a$$ and $$K_b$$ for a conjugate acid–base pair?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 14

Which of the following cations will make an aqueous solution acidic?

Accepted Answer

$$\mathrm{NH_4$^+}$$

Question 15

Which of the following statements about polyprotic acids is correct?

Accepted Answer

The $$K_a$$ value for the first dissociation is always larger than for the second.

Question 16

Which of the following best explains why carboxylic acids are generally stronger acids than alcohols?

Accepted Answer

Carboxylic acids have resonance stabilization in their conjugate base.

Question 17

A solution has $$[OH^-] = 1.0 	imes 10$$^{-3}$$\ \mathrm{M}. $$What is the pOH and pH of the solution at $$25^\circ\mathrm{C}$$?

Accepted Answer

$$pOH = 3.00$$, $$pH = 11.00$$

Question 18

Which of the following is true for the percent ionization of a weak acid as its concentration increases?

Accepted Answer

Percent ionization decreases.

Question 19

Which of the following best describes the effect of a highly charged metal cation (e.g., $$Fe^{3+}) on $$water?

Accepted Answer

It increases the acidity of the solution by polarizing and weakening the O–H bonds in water.

Acid–Base Equilibria: Concepts, Calculations, and Applications

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