Question 1

Which of the following best describes the role of water (H$$_2O) as an $$acid in the Brønsted-Lowry theory?

Accepted Answer

It loses a proton, so it is a proton donor.

Question 2

Given the following equilibrium: $$\mathrm{H_2BO_3^- (aq) + H_2O (l) \rightleftharpoons H_3BO_3 (aq) + OH^- (aq)}$$, what is the $$K_b$$ expression for this reaction?

Accepted Answer

$$K_b = \dfrac{[H_3BO_3][OH^-]}{[H_2BO_3^-]}$$

Question 3

A 0.27 M solution of acetic acid ($$\mathrm{CH_3COOH}) $$has a $$K_a of$$ $$1.3 	imes 10$$^{-5}$$. What is the pH at equilibrium?

Accepted Answer

2.73

Question 4

Which of the following salts will have a pH less than 7 when dissolved in water?

Accepted Answer

NH$$_4NO$_3$$

Question 5

A solution containing caffeine ($$\mathrm{C_8H_{10}N_4O_2}) $$has a hydroxide concentration of $$7.29 	imes 10$$^{-6}$$ M at equilibrium. What is the pH? Is it an acidic, basic, or neutral solution?

Accepted Answer

8.86, basic

Question 6

Which of the following pairs of compounds will form a buffer and have the greatest buffer capacity when combined?

Accepted Answer

0.10 M CH$$_3$$COOH and 0.25 M CH$$_3$$COONa

Question 7

If 42.0 mL of 0.100 M NaOH is required to completely neutralize 100.0 mL of triprotic phosphoric acid ($$\mathrm{H_3PO_4}) $$solution, what is the concentration of the acid?

Accepted Answer

0.1240 M

Question 8

A weak acid solution has a pH of 5.13. What is the $$[H_3O^+]$$ concentration?

Accepted Answer

$$1.3 	imes 10$$^{-5}$$ M

Question 9

What is the percent ionization of a 0.27 M solution of acetic acid ($$K_a = 1.3 	imes 10$$^{-5}$$)?

Accepted Answer

0.089%

Question 10

Which of the following statements is true regarding the relationship between $$K_a$$, $$K_b$$, and $$K_w$$?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 11

If the $$pK_a of an $$acid is 7.52 and the $$pK_b of $$its conjugate base is 6.64, what is the value of $$pK_w$$?

Accepted Answer

$$pK_w = 14.16$$

Question 12

A buffer solution is made by mixing 0.100 M acetic acid and 0.100 M sodium acetate. If the $$K_a$$ for acetic acid is $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer?

Accepted Answer

4.74

Question 13

Which of the following is the correct equilibrium constant expression for the weak acid $$\mathrm{HC_2H_3O_2}$$?

Accepted Answer

$$K_a = \dfrac{[C_2H_3O_2^-][H_3O^+]}{[HC_2H_3O_2]}$$

Question 14

A weak acid solution has a $$pH of 4.88. $$What is the $$[H_3O^+]$$ concentration?

Accepted Answer

$$1.3 	imes 10$$^{-5}$$ M$

Question 15

A buffer solution is prepared by mixing 0.100 M NH$$_3$$ and 0.100 M NH$$_4Cl. If $$the $$K_b$$ for NH$$_3 is$$ $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer?

Accepted Answer

9.25

Question 16

If 10.00 mL of 0.103 M HClO solution is titrated by 2.06 mL of 0.500 M NaOH solution, what is the pH at this point in the titration? Is the solution acidic, neutral, or basic?

Accepted Answer

7.00, neutral

Question 17

When a small amount of highly soluble NaOH is added to a solution of weak acid NH$$_4NO$_3$$, what will happen to the pH value after the following neutralization reaction: $$\mathrm{NH_4$^+ (aq) + OH^- (aq) \rightarrow NH_3$ (aq) + H_2O (l)}$$?

Accepted Answer

The pH value will increase since [OH$$^-$$] decreases.

Question 18

Given the following titration graph, Unknown 1 has an equivalence point at pH 7.0 and Unknown 2 at pH 2.0. What can you determine about these two unknown samples?

Accepted Answer

Unknown 1 is a stronger acid than Unknown 2, so $$K_a is $$greater than $$K_a.$$

Question 19

A buffer solution is made by mixing 0.100 M acetic acid and 0.100 M sodium acetate. If the $$K_a$$ for acetic acid is $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer?

Accepted Answer

4.74

Acids, Bases, Buffers, and Equilibrium: General Chemistry Study Guide

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