Question

A swimming-pool worker wants the pool's pH to be 7.2. She comes by to test the water and finds that the pH is 9.2. What should she do to correct this situation?

A. Add water.

B. Add base.

C. Add acid.

D. Do nothing.

Answer 1

The correct answer is option C.

Step-by-step explanation:

The pH of the solution is negative logarithm of hydrogen ion concentration in the aqueous solution.

`pH=-\log[H^+]`

• Higher the hydrogen ion concentration lower will be the pH.Hence, acidic
• Lower the hydrogen ion concentration higher will be the pH.Hence, alkaline.

The pH of the pool = 9.2

`9.2=-\log[H^+]`

`[H^+]=6.3096* 10^(-10) M`

The pH of the pool desired by worker = 7.2

`7.2=-\log[H^+]'`

`[H^+]'=6.3096* 10^(-8) M`

Hydrogen ion needed tom vahnge pH of the pool from 9.2 to 7.2 is

:
`[H^+]'-[H^+]=6.3096* 10^(-8) M-6.3096* 10^(-10) M`

`=6.2465* 10^(-8) M`

For hydrogen ions worker has to add acid which will give hydrogen ion in its aqueous from. Hence, correct answer is option C.

Answer 2

Answer : The correct option is, (C) Add acid.

Explanation :

As we know that, the pH measures the acidity and basicity of a substance.

The pH range for acidic solution is, 0.1 to 6.9

The pH range for basic solution is, 7.1 to 14

For neutral solution the pH is, 7

As per question, the worker wants the pH of the swimming pool is, 7.2 that means slightly basic. But by testing the water, she found that the pH is, 9.2 that means highly basic. So, to correct the pH of swimming pool that is 7.2 she should add an acid into the water to overcome the basicity of the water.

Hence, the correct option is, (C) Add acid.