Chapter 18, Problem 18.55P

a)

Interpretation Introduction

Interpretation: To determine whether the given concentration has an equal concentration of ${\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}]$ and $[{\text{CH}}_{\text{3}}{\text{COO}}^{\text{-}}]$

Concept introduction: ${\text{CH}}_{\text{3}}\text{COOH}$ is a weak acid and will not completely dissociate into ions. The concentration of ${\text{CH}}_{\text{3}}\text{COOH}$ is already given in the question and the ${\text{K}}_{\text{a}}$ value of ${\text{CH}}_{\text{3}}\text{COOH}$ is $1.8\times {10}^{-5}$ . Now, draw a reaction table and find the concentration of $[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}]$ and the $[{\text{CH}}_3{\text{COO}}^{\text{-}}]$ ions.

b)

Interpretation Introduction

Interpretation: To determine whether the given concentration has an equal concentration of ${\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}]$ and $[{\text{CH}}_{\text{3}}{\text{COO}}^{\text{-}}]$

Concept introduction: ${\text{CH}}_{\text{3}}\text{COOH}$ is a weak acid and will not completely dissociate into ions. The concentration of ${\text{CH}}_{\text{3}}\text{COOH}$ is already given in the question and the ${\text{K}}_{\text{a}}$ value of ${\text{CH}}_{\text{3}}\text{COOH}$ is $1.8\times {10}^{-5}$ . The self-ionization of water will come into play because water can act both as a base and as an acid.

c)

Interpretation Introduction

Interpretation: To determine whether the given concentration has an equal concentration of ${\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}]$ and $[{\text{CH}}_{\text{3}}{\text{COO}}^{\text{-}}]$

Concept introduction: ${\text{CH}}_{\text{3}}\text{COOH}$ is a weak acid and will not completely dissociate into ions. The concentration of ${\text{CH}}_{\text{3}}\text{COOH}$ is already given in the question and the ${\text{K}}_{\text{a}}$ value of ${\text{CH}}_{\text{3}}\text{COOH}$ is $1.8\times {10}^{-5}$ . Find the ${\text{pK}}_{\text{a}}$ value and then substitute this in the equation of pH.