   Chapter 16, Problem 16.92QP General Chemistry - Standalone boo...

11th Edition
Steven D. Gammon + 7 others
ISBN: 9781305580343

Solutions

Chapter
Section General Chemistry - Standalone boo...

11th Edition
Steven D. Gammon + 7 others
ISBN: 9781305580343
Textbook Problem

Sodium benzoate, NaC7H5O2, is used as a preservative in foods. Consider a 50.0-mL sample of 0.250 M NaC7H5O2 being titrated by 0.200 M HBr. Calculate the pH of the solution: a when no HBr has been added; b after the addition of 50.0 mL of the HBr solution; c at the equivalence point; d after the addition of 75.00 mL of the HBr solution. The Kb value for the benzoate ion is 1.6 × 10−10.

(a)

Interpretation Introduction

Interpretation:

The pH of the given points of the titration of sodium benzoate with HBr has to be calculated.

When no HBr has been added

Concept Introduction:

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion [OH] concentration.

pOH=-log[OH]

Relationship between pH  and pOH:

pH + pOH = 14

Explanation

To Calculate: The pH when no HBr has been added

Given data:

Sodium benzoate (NaC7H5O2) is used as preservatives in foods.

The volume of sodium benzoate = 50.0 mL

The concentration of sodium benzoate = 0.250 M

The concentration of HBr= 0.200 M

The Kb value for the benzoate ion is 1.6×1010

pH when noHBr has been added

Construct an equilibrium table for the hydrolysis of benzoate ion as follows,

 C7H5O2-  +   H2O  ⇌      HC7H5O2  +   OH− Initial (M) 0.250 −x 0.250-x 0.00 0.00 Change (M) +x +x Equilibrium (M) x x

The Kb value for the benzoate ion is 1.6×1010

Now substitute equilibrium concentrations into the equilibrium-constant expression

(b)

Interpretation Introduction

Interpretation:

The pH of the given points of the titration of sodium benzoate with HBr has to be calculated.

After the addition of 50.0 mL of HBr solution

Concept Introduction:

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion [OH] concentration.

pOH=-log[OH]

Relationship between pH  and pOH:

pH + pOH = 14

(c)

Interpretation Introduction

Interpretation:

The pH of the given points of the titration of sodium benzoate with HBr has to be calculated.

At the equivalence point

Concept Introduction:

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion [OH] concentration.

pOH=-log[OH]

Relationship between pH  and pOH:

pH + pOH = 14

(d)

Interpretation Introduction

Interpretation:

The pH of the given points of the titration of sodium benzoate with HBr has to be calculated.

After the addition of 75.00 mL of HBr solution

Concept Introduction:

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion [OH] concentration.

pOH=-log[OH]

Relationship between pH  and pOH:

pH + pOH = 14

Still sussing out bartleby?

Check out a sample textbook solution.

See a sample solution

The Solution to Your Study Problems

Bartleby provides explanations to thousands of textbook problems written by our experts, many with advanced degrees!

Get Started 