Acids, Bases & Aqueous Life Full Test Bank Chapter 17 4e

Chapter 17: Acids, bases, and buffer solutions: life in an aqueous environment

Test Bank

Type: multiple choice question

Title: Chapter 17 - Question 01

1) Which one of the following is the correct expression for the ion product of water?

a.

b.

c.

d.

e. log pH × log pOH

Type: multiple choice question

Title: Chapter 17 - Question 02

2) The pH of human blood is 7.4. Therefore the hydrogen ion concentration in human blood is which of the following?

a. 7.4 M

b. 2.5 × 10⁷ M

c. 1.6 × 10³ M

d. 4.0 × 10^–8 M

e. 7.4 × 10^–7 M

Type: multiple choice question

Title: Chapter 17 - Question 03

3) The pH of a 0.005 M solution of hydrobromic acid is which of the following?

a. 1.3

b. 2.1

c. 2.3

d. 2.0

e. 5.0

Type: multiple choice question

Title: Chapter 17 - Question 04

4) A solution of HCl at concentration of 4 × 10^–4 mol L^–1 has a pH of which of the following?

a. 2.67

b. 3.21

c. 3.40

d. 4.31

e. 4.0

Type: multiple choice question

Title: Chapter 17 - Question 05

5) The conjugate base of the acid H₂PO₄^– is which of the following?

a. H₃PO₄

b. HPO₄^–

c. HPO₄^2–

d. H₂PO₄^2–

e. H₃PO₄^–

Type: multiple choice question

Title: Chapter 17 - Question 06

6) Given the pK_a for ammonium ion is 9.26, what is the pH of 1 L of
solution which contains 5.35 g of NH₄Cl, and contains the ammonium ion at a concentration of 0.2 mol L^-1? (Molar mass of NH₄Cl = 54.5 g mol^–1.)

a. 7.00

The 0.098 mol of NH₄Cl are present in 1 L, giving a concentration of 0.098 mol L^-1.

We can now feed all the numbers into the Henderson-Hasselbalch equation:

pH = pK_a + log

= 9.26 + log

= 9.26 + log 2.0408

= 9.26 + 0.3

= 9.56

b. 7.65

The 0.098 mol of NH₄Cl are present in 1 L, giving a concentration of 0.098 mol L^-1.

We can now feed all the numbers into the Henderson-Hasselbalch equation:

pH = pK_a + log

= 9.26 + log

= 9.26 + log 2.0408

= 9.26 + 0.3

= 9.56

c. 8.96

The 0.098 mol of NH₄Cl are present in 1 L, giving a concentration of 0.098 mol L^-1.

We can now feed all the numbers into the Henderson-Hasselbalch equation:

pH = pK_a + log

= 9.26 + log

= 9.26 + log 2.0408

= 9.26 + 0.3

= 9.56

d. 9.56

The 0.098 mol of NH₄Cl are present in 1 L, giving a concentration of 0.098 mol L^-1.

We can now feed all the numbers into the Henderson-Hasselbalch equation:

pH = pK_a + log

= 9.26 + log

= 9.26 + log 2.0408

= 9.26 + 0.3

= 9.56

e. 9.95

The 0.098 mol of NH₄Cl are present in 1 L, giving a concentration of 0.098 mol L^-1.

We can now feed all the numbers into the Henderson-Hasselbalch equation:

pH = pK_a + log

= 9.26 + log

= 9.26 + log 2.0408

= 9.26 + 0.3

= 9.56

Type: multiple choice question

Title: Chapter 17 - Question 07

7) Which of the following acids would you use to make an effective buffer for a reaction at pH 8?

a. Ethanoic acid; K_a = 1.7 × 10^–5

We also need to remember that pK_a = -log K_a (see section 17.2). So the pK_a of ethanoic acid is 4.80: it buffers at a pH of 4.8, not 8.

b. Diphosphoric acid; K_a = 1.4 × 10^–7

We also need to remember that pK_a = -log K_a (see section 17.2). So the pK_a of diphosphoric acid is 6.85: it buffers at a pH of 6.85, not 8.

c. Tris-hydroxmethylaminoethane; K_a = 8.3 × 10^–9

We also need to remember that pK_a = -log K_a (see section 17.2). So the pK_a of Tris-hydroxmethylaminoethane is 8.0: it buffers at a pH of 8.0, which is what we need in this instance.

d. Ammonium chloride; K_a = 5.6 × 10^–10

We also need to remember that pK_a = -log K_a (see section 17.2). So the pK_a of ammonium chloride is 9.3: it buffers at a pH of 9.3, not 8.

e. Sodium bicarbonate; K_a = 5.3 × 10^–11

We also need to remember that pK_a = -log K_a (see section 17.2). So the pK_a of sodium bicarbonate is 10.3: it buffers at a pH of 10.3, not 8.

Type: multiple choice question

Title: Chapter 17 - Question 08

8) A 0.1 M solution of ethanoic acid is 1.34% ionized. What is the value of K_a for ethanoic acid?

a. K_a = 5.3 × 10^–11

We know that, in general terms, .

So, in this instance, = 1.82 × 10^-5

b. K_a = 1.82 × 10^–5

We know that, in general terms, .

So, in this instance, = 1.82 × 10^-5

c. K_a = 1.34 × 10^–6

We know that, in general terms, .

So, in this instance, = 1.82 × 10^-5

d. K_a = 2.67 × 10^–2

We know that, in general terms, .

So, in this instance, = 1.82 × 10^-5

e. K_a = 3.01 × 10^–4

We know that, in general terms, .

So, in this instance, = 1.82 × 10^-5

Type: multiple choice question

Title: Chapter 17 - Question 09

9) If the concentration of [OH^–] in an aqueous solution is 0.3 M, what is the pH of that solution?

a. 8.96

If we know that [OH^-] = 0.3 mol L^-1, then [H⁺] = (1 × 10^-14)/0.3 = 3.33 × 10^-14.

Now, pH = - log [H⁺] = - log 3.33 × 10^-14 = 13.48.

b. 10.87

If we know that [OH^-] = 0.3 mol L^-1, then [H⁺] = (1 × 10^-14)/0.3 = 3.33 × 10^-14.

Now, pH = - log [H⁺] = - log 3.33 × 10^-14 = 13.48.

c. 1.45

If we know that [OH^-] = 0.3 mol L^-1, then [H⁺] = (1 × 10^-14)/0.3 = 3.33 × 10^-14.

Now, pH = - log [H⁺] = - log 3.33 × 10^-14 = 13.48.

d. 3.67

If we know that [OH^-] = 0.3 mol L^-1, then [H⁺] = (1 × 10^-14)/0.3 = 3.33 × 10^-14.

Now, pH = - log [H⁺] = - log 3.33 × 10^-14 = 13.48.

e. 13.48

If we know that [OH^-] = 0.3 mol L^-1, then [H⁺] = (1 × 10^-14)/0.3 = 3.33 × 10^-14.

Now, pH = - log [H⁺] = - log 3.33 × 10^-14 = 13.48.

Type: matching question

Title: Chapter 17 - Question 10

10) Look at the following equilibrium reaction:

Match each chemical species with the term that best describes its role in this reaction scheme.

Feedback: To remind yourself about conjugate acid-base pairs, look at section 17.1.

a. Conjugate acid = C

b. Acid = B

c. Base = A

d. Conjugate base = D

Type: multiple response question

Title: Chapter 17 - Question 11

11) Which of the following reactions depict the behaviour of an acid? Select any that apply.

a. NH₃ + H⁺ ⇌ NH₄⁺

b. CH₃COO^- + H⁺ ⇌ CH₃COOH

c. CH₃COOH ⇌ CH₃COO^- + H⁺

d. H₂O ⇌ H⁺ + OH^-

e. H₂O + H⁺ ⇌ H₃O⁺

Type: multiple choice question

Title: Chapter 17 - Question 12

12) Which of the following depicts a neutralization reaction?

a. CH₃CH₂COOH ⇌ CH₃CH₂COO^– + H⁺

b. CH₃CH₂COOH + NaOH 🡪 CH₃CH₂COONa + H₂O

c. CH₃CH₂COOH + CH₃OH 🡪 CH₃CH₂COOCH₃ + H₂O

d. CH₃CH₂COOH + H₂O ⇌ CH₃CH₂COO^– + H₃O⁺

Type: multiple choice question

Title: Chapter 17 - Question 13

13) Which of the following is the weakest acid?

a. Boric acid, K_a = 7.3 × 10^-10

b. Benzoic acid, K_a = 6.3 × 10^-5

c. Sulfurous acid, K_a = 1.2 × 10^-2

d. Ethanoic acid, K_a = 1.8 × 10^-5

e. Formic acid, K_a = 1.8 × 10^-4

Type: multiple response question

Title: Chapter 17 - Question 14

14) Which of the following statements about buffer solutions are true? Select any that apply.

First, a buffer solution does not have to contain a strong acid. Instead, it must contain a weak acid (or a weak base) – a strong acid wouldn’t be appropriate. Look at section 17.7 for more details.

Second, The conjugate acid present in the buffer solution does not consume excess H⁺ ions. Instead, it is the conjugate base that consumes excess H⁺ ions.

a. A buffer solution must contain a strong acid.

b. A buffer solution undergoes a neutralization reaction to consume excess OH^- ions.

c. The conjugate acid present in the buffer solution consumes excess H⁺ ions.

d. The components of the buffer solution must be present at high concentrations.

e. A buffer solution can only resist changes in pH when small quantities of an acid or base are added to it.

Type: matching question

Title: Chapter 17 - Question 15

15) Match the type of compound with the biological environment into which it is most likely to partition.

Feedback: Strong acids have a greater tendency to become ionized than weak acids, and ionized compounds are more likely to partition into an aqueous, hydrophilic environment (such as the bloodstream) than a hydrophobic environment (such as a lipid membrane).

Page reference: section 17.6

a. Strong acid = Bloodstream

b. Weak acid = Lipid membrane

Type: matching question

Title: Chapter 17 - Question 16

16) Match the following amino acids with the most appropriate description of the extent of ionization of their side chains when the pH of their environment has a value of 10.0

Page reference: section 17.6

a. Lysine (pK_a 10.5) = Roughly 50% ionized

b. Arginine (pK_a 12.5) = Less than 50% ionized

c. Glutamic acid (pK_a 4.1) = More than 50% ionized