Chapter 22.2, Problem 11R

To determine

The way to adjust the pH of the pool if its pH is $8.2$ and $6.9$ .

Explanation of Solution

Introduction:

The pH of a solution is a measure of the concentration of ${\text{H}}^{+}$ ions within the solution.

If pH $\text{<7}$ , the solution is described as acidic.

If pH $\text{=7}$ , the solution is neutral.

If pH $\text{>7}$ , the solution is basic.

Of the substances added to the pool, ${\text{Na}}_2{\text{CO}}_3$ is a base, whereas $\text{HCl}$ is an acid.

If the pool’s pH is $8.2$ , the water is slightly basic and so to regulatethe pH to the given range ( $7.2\text{-}7.8$ ), $\text{HCl}$ can be used. $\text{HCl}$ , being a strong acid, lowers the pH of the alkaline water.

However, if the pool’s pH is $6.9$ , the water is slightly acidic and so to adjust the pH to the given range ( $7.2\text{-}7.8$ ), ${\text{Na}}_2{\text{CO}}_3$ can be used. ${\text{Na}}_2{\text{CO}}_3$ , being slightlybasic, increases the pH of the acidic water.

Conclusion: If the pool’s pH is $8.2$ , $\text{HCl}$ being a strong acid, can be used to lower the pH of the water to the pH range $7.2\text{-}7.8$ .

However, if the pool’s pH is $6.9$ , ${\text{Na}}_2{\text{CO}}_3$ being slightly basic, can be used to increase the pH of the water.