Chapter 17.2, Problem 3RC

Interpretation Introduction

Interpretation:

The value of $\text{pH}$ is to be calculated for the given mixture which contains $100\text{mL}$ ammonium chloride $\left(0.02\text{mol}\cdot {\text{L}}^{-1}\right)$ and $200\text{mL}$ ammonia $\left(0.02\text{mol}\cdot {\text{L}}^{-1}\right)$ solutions.

Concept introduction:

A buffer is defined as a solution which does not show any change in its $\text{pH}$ values on addition of small amount of acid or base. There are two types of buffer solutions, (1) Acidic Buffer and (2) Basic Buffer.

Acidic Buffer is a solution which has the $\text{pH}$ value below $7$. An acidic buffer is prepared by mixing a weak acid with its conjugate base. For example a mixture of weak acid ${\text{CH}}_3\text{COOH}$ and its conjugate base ${\text{CH}}_3{\text{COO}}^{-}$ gives a acidic buffer.

${\text{CH}}_3\text{COOH}\left(\text{aq}\text{.}\right){\text{+ H}}_{\text{2}}\text{O}\left(\text{l}\right)\rightleftharpoons {\text{H}}_{\text{3}}{\text{O}}^{+}\left(\text{aq}\text{.}\right){\text{+ CH}}_3{\text{COO}}^{-1}\left(\text{aq}\text{.}\right)$

Basic Buffer is a solution which has the $\text{pH}$ value above $7$. A basic buffer is prepared by mixing a weak base with its conjugate acid. For example a mixture of weak base ${\text{NH}}_4\text{OH}$ and its conjugate acid ${\text{NH}}_4{}^{+}$ gives a baisc buffer.

${\text{NH}}_4\text{OH}\left(\text{aq}\text{.}\right)\rightleftharpoons {\text{NH}}_4{}^{+}\left(\text{aq}\text{.}\right){\text{+ OH}}^{-1}\left(\text{aq}\text{.}\right)$