Chapter 14, Problem 66E

Interpretation Introduction

Interpretation:

The concentration of ${\text{H}}_3{\text{O}}^{+}$ is to be calculated and each of the given solutions is to be classified as an acidic or basic.

Concept Introduction:

In a neutral solution, the concentrations of both ${\text{H}}_3{\text{O}}^{+}$ and ${\text{OH}}^{-}$ are equal. The concentration of the neutral solution is:

$\begin{array}{c}\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]=\left[{\text{OH}}^{-}\right]\\ =1.0\times {10}^{-7}\text{ M}\end{array}$

The concentration of ${\text{H}}_3{\text{O}}^{+}$ increases in acidic solution. The expression is:

$\begin{array}{c}\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]>1.0\times {10}^{-7}\text{ M }\\ \left[{\text{OH}}^{-}\right]<1.0\times {10}^{-7}\text{ M}\end{array}$

The concentration of ${\text{OH}}^{-}$ increases in basic solution. The expression is:

$\begin{array}{c}\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]<1.0\times {10}^{-7}\text{ M }\\ \left[{\text{OH}}^{-}\right]>1.0\times {10}^{-7}\text{ M}\end{array}$

In an aqueous solution, the product of concentrations of ${\text{H}}_3{\text{O}}^{+}$ and ${\text{OH}}^{-}$ is known as ionic product constant for water $\left(K_{\text{w}}\right)$.

The value of $K_{\text{w}}$ at ${25}^{\circ }\text{ C}$ is $1.0\times {10}^{-14}\text{ M}$.