Chapter 16, Problem 111QP

Interpretation Introduction

Interpretation:

The pH of the solution with a dissolved salt is to be predicted.

Concept Introduction:

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

When a salt contains a cation that comes from a weak base, the cation recombines with water to produce a weak base and hydronium ions and forms an acidic solution.

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 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 p^H of the solution.

The cations that are highly charged and are of a small size form acidic solutions.

The cations from group 1A and selective cations of group 2A, along with the ones from strong bases, will form neutral solutions.

When the cation as well as the anion of the salt hydrolysis, the ionization constant of the species decides the p^H of the solution.

For $K_{\text{a}}>K_{\text{b}}$, the solution is acidic.

For $K_{\text{a}}<K_{\text{b}}$, the solution is basic.

For $K_{\text{a}}=K_{\text{b}}$, the solution is neutral.

Here, $K_{\text{a}}=$ ionization constant of acid.

$K_{\text{b}}=$ ionization constant of base.

The relationship between $K_{\text{a}}\text{ and }{K}_{\text{b}}$ of a weak acid and its conjugate base, or vice versa, is

$K_{\text{w}}=K_{\text{a}}\times K_{\text{b}}$ …… (1)