   Chapter 17, Problem 29PS

Chapter
Section
Textbook Problem

You require 36.78 mL of 0.0105 M HCl to reach the equivalence point in the titration of 25.0 mL of aqueous ammonia. (a) What was the concentration of NH3 in the original ammonia solution? (b) What are the concentrations of H3O+, OH−, and NH4+ at the equivalence point? (c) What is the pH of the solution at the equivalence point?

(a)

Interpretation Introduction

Interpretation:

For the titration between NH3 and HCl. The concentration of original NH3 solution has to be calculated.

Concept introduction:

Titration is a quantitative method to determine the quantity of an acid or base in a solution.

For strong acid-weak base titration the pH value can be calculated at various points before and after equivalence point. The equilibrium established during the titration of NH3 with HCl is represented as,

NH3(aq)+ H3O+(aq)H2O(l)+NH4+(aq)

Explanation

Calculation of concentration is given below.

Given:

The concentration of HCl is 0.0105 molL1.

The volume of HCl used is 36.78 mL or 0.03678 L.

The volume of ammonia titrated is 25 mL or 0.025 L.

The concentration of ammonia is calculated as,

Expression used for the neutralization is as follows,

C1V1=C2V2

Here,

• C1 is the concentration of ammonia.
• V1 is the volume of ammonia.
• C2 is the concentration of HCl used.
• V2 is the volume of HCl used for the neutralization.

Substitute 0.03678 L for V2, 0.025 L for V1,0.0105 molL1 for C2

(b)

Interpretation Introduction

Interpretation:

For the titration between NH3 and HCl. The concentration of OH,H3O+, and NH4+ is to be calculated at equivalence point. has to be calculated.

Concept introduction:

Titration is a quantitative method to determine the quantity of an acid or base in a solution.

For strong acid-weak base titration the pH value can be calculated at various points before and after equivalence point. The equilibrium established during the titration of NH3 with HCl is represented as,

NH3(aq)+ H3O+(aq)H2O(l)+NH4+(aq)

(c)

Interpretation Introduction

Interpretation:

For the titration between NH3 and HCl. The value of pH at equivalence point has to be calculated.

Concept introduction:

Titration is a quantitative method to determine the quantity of an acid or base in a solution.

For strong acid-weak base titration the pH value can be calculated at various points before and after equivalence point. The equilibrium established during the titration of NH3 with HCl is represented as,

NH3(aq)+ H3O+(aq)H2O(l)+NH4+(aq)

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