Chapter 16.22, Problem 1PPC

Interpretation Introduction

Interpretation:

All the reactions that represent the effect on the pH of a solution of salt and water are to be identified.

Concept introduction:

Salt is a strong electrolyte that dissociates completely when added to water.

When a salt contains an anion that comes from a weak acid, the anion recombines with water to produce a weak acid and hydroxide ions, and forms a basic solution. If a cation comes from a strong base, it does not recombine, and is present in the solution as a free ion, without having any effect on the pH of the solution.

The reaction of the salt $\left(\text{BA}\right)$ that takes place is:

${\text{A}}^{-}{}_{\left(\text{aq}\right)}+{\text{H}}_2{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons {\text{HA}}_{\left(\text{aq}\right)}+{\text{OH}}^{-}{}_{\left(\text{aq}\right)}$

When a salt contains a cationthatcomes from a weak base, the cation recombines with water to produce a weak base and hydronium ions, and forms an acidic solution. If the anion comes from a strong acid, it does not recombine, and is present in the solution as a free ion, without having any effect on the pH of the solution.

The reaction of the salt that takes place is:

${\text{BH}}^{+}{}_{\left(\text{aq}\right)}+{\text{H}}_2{\text{O}}_{\left(\text{l}\right)}\rightleftharpoons {\text{B}}_{\left(\text{aq}\right)}+{\text{H}}_3{\text{O}}^{+}{}_{\left(\text{aq}\right)}$