   # a. Calculate the pH of a buffered solution that is 0.100 M in C 6 H 5 CO 2 H (benzoic acid, K a = 6.4 × 10 −5 ) and 0.100 M in C 6 H 5 CO 2 Na. b. Calculate the pH after 20.0% (by moles) of the benzoic acid is converted to benzoate anion by addition of a strong base. Use the dissociation equilibrium C 6 H 5 CO 2 H(aq) ⇌ C 6 H 5 CO 2 - (aq) + H + (aq) to calculate the pH. c. Do the same as in part b, but use the following equilibrium to calculate the pH: C 6 H 5 CO 2 - (aq) + H 2 O(l) ⇌ C 6 H 5 CO 2 H(aq) + OH - (aq) d. Do your answers in parts b and c agree? Explain. ### Chemistry: An Atoms First Approach

2nd Edition
Steven S. Zumdahl + 1 other
Publisher: Cengage Learning
ISBN: 9781305079243

#### Solutions

Chapter
Section ### Chemistry: An Atoms First Approach

2nd Edition
Steven S. Zumdahl + 1 other
Publisher: Cengage Learning
ISBN: 9781305079243
Chapter 14, Problem 82AE
Textbook Problem
1 views

## a. Calculate the pH of a buffered solution that is 0.100 M in C6H5CO2H (benzoic acid, Ka = 6.4 × 10−5) and 0.100 M in C6H5CO2Na.b. Calculate the pH after 20.0% (by moles) of the benzoic acid is converted to benzoate anion by addition of a strong base. Use the dissociation equilibriumC6H5CO2H(aq) ⇌ C6H5CO2-(aq) + H+(aq)to calculate the pH.c. Do the same as in part b, but use the following equilibrium to calculate the pH:C6H5CO2-(aq) + H2O(l) ⇌ C6H5CO2H(aq) + OH-(aq)d. Do your answers in parts b and c agree? Explain.

(a)

Interpretation Introduction

Interpretation:

The pH value of the given solutions is to be calculated.

Concept introduction:

A solution that resists a change in the pH on addition of an acid or an alkali is termed as a buffer solution.

The pH of a solution is defined as a figure that expresses the acidity of the alkalinity of a given solution.

### Explanation of Solution

Explanation

Given

The concentration of benzoic acid is 0.100M .

The concentration of sodium benzoate is 0.100M .

The Ka of benzoic acid is 6.4×105 .

The relation between pH and pKa is given by Henderson-Hasselbach equation. According to this equation,

pH=pKa+log[Salt][Acid]

The value of pKa is calculated by the formula,

pKa=log(Ka)

Substitute the value of pKa in the Henderson-Hasselbach equation

(b)

Interpretation Introduction

Interpretation:

The pH value of the given solutions is to be calculated.

Concept introduction:

A solution that resists a change in the pH on addition of an acid or an alkali is termed as a buffer solution.

The pH of a solution is defined as a figure that expresses the acidity of the alkalinity of a given solution.

(c)

Interpretation Introduction

Interpretation:

The pH value of the given solutions is to be calculated.

Concept introduction:

A solution that resists a change in the pH on addition of an acid or an alkali is termed as a buffer solution.

The pH of a solution is defined as a figure that expresses the acidity of the alkalinity of a given solution.

(d)

Interpretation Introduction

Interpretation:

The pH value of the given solutions is to be calculated.

Concept introduction:

A solution that resists a change in the pH on addition of an acid or an alkali is termed as a buffer solution.

The pH of a solution is defined as a figure that expresses the acidity of the alkalinity of a given solution.

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