Chapter U4.17, Problem 3E

Interpretation Introduction

Interpretation:

A substance with a neutral pH needs to be explained.

Concept introduction:

The pH is the property of a solution that describes the acidity or alkalinity of the solution.

Answer to Problem 3E

A substance has neutral pH means $\left[{\text{H}}^{\text{+}}\right]\text{ = }\left[{\text{OH}}^{\text{-}}\right]$ for the solution.

Explanation of Solution

At 298 K,

  $\text{pH+pOH=14}.$

Thus in the neutral condition,

  $\text{pH=pOH=7}.$ .

The pH is related to hydrogen ion concentration as follows:

  $\text{pH}=-\log \left[{\text{H}}^{+}\right]$

Similarly, pOH is:

  $\text{pOH}=-\log \left[{\text{OH}}^{-}\right]$

Thus,

  $\left[{\text{H}}^{\text{+}}\right]\text{ = }\left[{\text{OH}}^{\text{-}}\right]$