Q: A solution has a pH of 3.0 at 25°C. What is the concentration of hydronium ions in this solution?

$$[H_3O^+] = 1.0 \times 10$$^{-3}$$~\mathrm{M}$$

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 Brønsted–Lowry acid and a Brønsted–Lowry base.

Question 3

Which of the following is the correct equilibrium expression for the autoionization of water?

Accepted Answer

$$K_w = [H_3O^+][OH^-]$$

Question 4

A solution has a pH of 3.0 at 25°C. What is the concentration of hydronium ions in this solution?

Accepted Answer

$$[H_3O^+] = 1.0 	imes 10$$^{-3}$$~\mathrm{M}$$

Question 5

Which of the following acids is considered a strong acid?

Accepted Answer

Hydrochloric acid ($$HCl)$$

Question 6

Calculate the pH of a $$0.010~\mathrm{M}$$ solution of $$HNO_3 (a $$strong acid) at 25°C.

Accepted Answer

pH = 2.00

Question 7

Which of the following best explains why $$HF is a $$weak acid while $$HCl is a $$strong acid?

Accepted Answer

$$HF$$ has a stronger H–F bond, making it harder to ionize.

Question 8

A $$0.10~\mathrm{M}$$ solution of formic acid ($$HCOOH) $$has a pH of 2.38. What is the acid dissociation constant $$K_a$$ for formic acid?

Accepted Answer

$$K_a = 1.8 	imes 10$$^{-5}$$

Question 9

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

Accepted Answer

Sodium acetate ($$NaCH_3COO)$$

Question 10

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 11

Which of the following is the correct relationship between $$K_a$$, $$K_b$$, and $$K_w$$ for a conjugate acid–base pair at 25°C?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 12

Which of the following best describes a Lewis acid?

Accepted Answer

A substance that accepts an electron pair.

Question 13

A solution is prepared by dissolving $$0.15~\mathrm{M}$$ $$NH_3 in $$water. Given $$K_b = 1.8 	imes 10$$^{-5}$$, what is the pH of the solution at 25°C?

Accepted Answer

pH = 11.20

Question 14

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

Accepted Answer

Decreasing bond strength between H and X.

Question 15

Which of the following is true for the conjugate base of a strong acid?

Accepted Answer

It has negligible basicity in water.

Question 16

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

Accepted Answer

The carboxylate anion is stabilized by resonance.

Question 17

A solution contains $$[H_3O^+] = 2.3 	imes 10$$^{-3}$$~\mathrm{M}. $$What is the pH of the solution?

Accepted Answer

pH = 2.64

Question 18

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

Accepted Answer

$$Fe^{3+}$$

Question 19

Which of the following statements about the effect of electronegativity on oxyacid strength is correct?

Accepted Answer

As the electronegativity of the central atom increases, the acid strength increases.

Acid–Base Equilibria: Concepts, Calculations, and Applications

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