Chapter 19, Problem 62A

Interpretation Introduction

Interpretation : The pH of pure water at room temperature is equal to 7.0 is to be explained.

Concept Introduction : The negative logarithm of the concentration of hydrogen ions is the pH of a solution. The values from 0 to 14 are the range of a pH scale.

Answer to Problem 62A

The pH of pure water at room temperature is equal to 7.0 due to the neutral nature of the solution and the concentration of hydrogen ion is $\text{1}\text{.0}\times {\text{10}}^{-7}\text{M}$ .

Explanation of Solution

The formula to calculate pH is given as

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

Here, ${\text{H}}^{\text{+}}$ denotes the concentration of hydrogen ion.

The concentration of hydrogen ions in pure water at room temperature is $\text{1}\text{.0}\times {\text{10}}^{-7}\text{M}$ .

To calculate the pH, substitute the values in the above formula:

  $\begin{array}{c}\text{pH=}-{\text{log[H}}^{\text{+}}\text{]}\\ \text{=}-\log \left[\text{1}\text{.0}\times {\text{10}}^{-7}\text{M}\right]\\ =7.00\end{array}$

A pH of 7.0 indicates a neutral solution.