Chapter 19.5, Problem 49LC

Interpretation Introduction

Interpretation : The pair of solutions that can form a buffer solution is to be identified.

Concept Introduction : A buffer is a solution that retains the pH of a solution irrespective of the addition of small amounts of acids or bases.

Answer to Problem 49LC

  ${\text{NH}}_{\text{3}}$ and ${\text{HCO}}_3^{-}$ pair does not form a buffer solution.

Explanation of Solution

A weak acid and one of its salts or a weak base and one of its salts are solutions that are used as buffers.

Buffers are formed by the combination of weak acids or bases with their respective salts.

The pair of solutions is ${\text{NH}}_{\text{3}}$ and ${\text{HCO}}_3^{-}$ .

The hydrogen carbonate ion and ammonia do not represent a conjugate pair.

It is ideal to have just one weak conjugate acid-base pair in a buffer for the maximum capacity.

Interpretation Introduction

Interpretation : The pair of solutions that can form a buffer solution is to be identified.

Concept Introduction : A buffer is a solution that retains the pH of a solution irrespective of the addition of small amounts of acids or bases.

Answer to Problem 49LC

  ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}\text{COOH}$ and ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{\text{COO}}^{-}$ pair form a buffer solution.

Explanation of Solution

A weak acid and one of its salts or a weak base and one of its salts are solutions that are used as buffers.

Buffers are formed by the combination of weak acids or bases with their respective salts.

The pair of solutions is ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}\text{COOH}$ and ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{\text{COO}}^{-}$ .

Benzoic acid and benzoate ions are a conjugate pair.

  ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}\text{COOH}+{\text{OH}}^{-}\rightleftharpoons {\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{\text{COO}}^{-}+{\text{H}}_{\text{2}}\text{O}$

  ${\text{C}}_{\text{6}}{\text{H}}_{\text{5}}{\text{COO}}^{-}+{\text{H}}^{+}\rightleftharpoons {\text{C}}_{\text{6}}{\text{H}}_{\text{5}}\text{COOH}$