   Chapter 14, Problem 97E

Chapter
Section
Textbook Problem

# Calculate [OH–], [H+], and the pH of 0.20 M solutions of each of the following amines. a. triethylamine [(C2H5)3N, Kb = 4.0 × 10–4] b. hydroxylamine (HINH2, Kb = 1.1 × 10–8)

(a)

Interpretation Introduction

Interpretation: [OH-],[H+]andpH for the given set has to be calculated.

Concept Introduction:

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

The pOH of a solution is calculated by the formula, pOH=log[OH]

The sum, pH+pOH=14

At equilibrium, the equilibrium constant expression is expressed by the formula,

Kb=ConcentrationofproductsConcentrationofreactants

Explanation

To determine: The pH,[H+] and [OH] of (C2H5)3N .

The equilibrium constant expression for the given reaction is,

Kb=[(C2H5)3NH+][OH][(C2H5)3N]

The reaction involved is,

(C2H5)3N(aq)+H2O(l)(C2H5)3NH+(aq)+OH(aq)

At equilibrium, the equilibrium constant expression is expressed by the formula,

Kb=ConcentrationofproductsConcentrationofreactants

Where,

• Kb is the base ionization constant.

The equilibrium constant expression for the given reaction is,

Kb=[(C2H5)3NH+][OH][(C2H5)3N]

The change in concentration of (C2H5)3N is assumed to be x .

The liquid components do not affect the value of the rate constant.

(C2H5)3N(aq)(C2H5)3NH+(aq)+OH(aq)Inititialconcentration0.2000Changex+x+xEquilibriumconcentration0.20xxx

The equilibrium concentration of [(C2H5)3N] is (0.20x)M .

The equilibrium concentration of [(C2H5)3NH+] is xM .

The equilibrium concentration of [OH] is xM

(b)

Interpretation Introduction

Interpretation: [OH-],[H+]andpH for the given set has to be calculated.

Concept Introduction:

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

The pOH of a solution is calculated by the formula, pOH=log[OH]

The sum, pH+pOH=14

At equilibrium, the equilibrium constant expression is expressed by the formula,

Kb=ConcentrationofproductsConcentrationofreactants

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