Q: Which equation correctly represents the Henderson-Hasselbalch equation for a buffer made from a weak acid and its conjugate base?

$pH = pK_a + \log \left( \frac{[\text{base}]}{[\text{acid}]} \right)$

Q: Which of the following best explains why a buffer resists changes in pH when a small amount of strong acid is added?

The strong acid is neutralized by the conjugate base in the buffer

Q: A student titrates 100.0 mL of 0.100 M acetic acid with 0.100 M KOH. What is the main species present at the equivalence point?

Acetate ion ($\mathrm{CH_3COO^-}$)

Q: Which of the following statements is TRUE regarding the titration of a weak acid with a strong base?

The pH at the equivalence point is greater than 7

Q: Which of the following is the correct expression for the ionization constant ($K_a$) of a weak acid $HA$?

$K_a = \frac{[H^+][A^-]}{[HA]}$

Q: Which of the following best describes the titration curve of a weak acid with a strong base?

The equivalence point occurs at pH greater than 7

Question 1

Which of the following combinations will produce a buffer solution?

Accepted Answer

CH3COOH and CH3COONa

Question 2

A buffer solution is prepared by mixing 0.15 M acetic acid ($\mathrm{CH_3COOH}$) and 0.15 M sodium acetate ($\mathrm{CH_3COONa}$). If the $K_a$ for acetic acid is $1.8 	imes 10^{-5}$, what is the pH of the buffer? Use the Henderson-Hasselbalch equation.

Accepted Answer

$pH = 4.74$

Question 3

Which equation correctly represents the Henderson-Hasselbalch equation for a buffer made from a weak acid and its conjugate base?

Accepted Answer

$pH = pK_a + \log \left( \frac{[	ext{base}]}{[	ext{acid}]} ight)$

Question 4

A buffer solution contains 0.100 M ammonia ($\mathrm{NH_3}$) and 0.250 M ammonium chloride ($\mathrm{NH_4Cl}$). If $K_b = 1.8 	imes 10^{-5}$, what is the pH of the solution?

Accepted Answer

$pH = 8.9$

Question 5

If 0.020 mol of HCl gas is added to 1.00 L of a buffer solution containing 0.100 M $\mathrm{NH_3}$ and 0.250 M $\mathrm{NH_4Cl}$, what happens to the pH?

Accepted Answer

The pH decreases slightly

Question 6

Which of the following best describes the common ion effect?

Accepted Answer

The suppression of the ionization of a weak acid or base by the addition of a salt containing a common ion

Question 7

Refer to the first titration curve image. What type of titration does this curve represent?

Accepted Answer

Titration of a strong acid with a strong base

Question 8

Refer to the second titration curve image. At what approximate pH does the equivalence point occur for the titration of acetic acid with NaOH?

Accepted Answer

$pH \approx 9$

Question 9

Which indicator would be most appropriate for detecting the endpoint in the titration of a strong acid with a strong base?

Accepted Answer

Litmus (pH range 4.7–8.2)

Question 10

A solution is initially 0.100 M in HOCl and 0.300 M in NaOCl. What is the pH if 0.030 mol of solid NaOH is added to 1.00 L of this solution? ($K_a = 3.5 	imes 10^{-8}$)

Accepted Answer

$pH = 8.18$

Question 11

What is the pH at the equivalence point of a titration of a strong acid with a weak base?

Accepted Answer

$pH < 7$

Question 12

Which of the following combinations will NOT produce a buffer solution?

Accepted Answer

HCN and NaCl

Question 13

What is the pH of a solution formed from the addition of 10.00 mL of 0.250 M NaOH to 25.00 mL of 0.200 M HF? ($K_a = 6.6 	imes 10^{-4}$)

Accepted Answer

$pH = 3.18$

Question 14

Which of the following best explains why a buffer resists changes in pH when a small amount of strong acid is added?

Accepted Answer

The strong acid is neutralized by the conjugate base in the buffer

Question 15

A student titrates 100.0 mL of 0.100 M acetic acid with 0.100 M KOH. What is the main species present at the equivalence point?

Accepted Answer

Acetate ion ($\mathrm{CH_3COO^-}$)

Question 16

Which of the following statements is TRUE regarding the titration of a weak acid with a strong base?

Accepted Answer

The pH at the equivalence point is greater than 7

Question 17

Which of the following is the correct expression for the ionization constant ($K_a$) of a weak acid $HA$?

Accepted Answer

$K_a = \frac{[H^+][A^-]}{[HA]}$

Question 18

A buffer is made by mixing 0.100 M acetic acid and 0.0500 M sodium acetate. What is the pH? ($K_a = 1.8 	imes 10^{-5}$)

Accepted Answer

$pH = 4.44$

Question 19

Which of the following best describes the titration curve of a weak acid with a strong base?

Accepted Answer

The equivalence point occurs at pH greater than 7

Chapter 7A Study Guide

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