Question

How does hypochlorous acid act as a disinfectant?

Explain the impact of low and high pH on the amount of hypochlorous acid in solution.

Why must the pH of a swimming pool be maintained between 7.2 and 7.8?

What chemicals can be used if the pH is too high? What chemicals can be used if the pH is too low?

Answer 1

1) When chlorine is added to the water, it forms Hypochlorous acid (HOCl), which itself dissociate to hypochlorite ions. Hypochlorous acid strongly oxidizes micro-organisms and kills them.Also it is naturally produced in white blood cells of all mammals which kills bacteria,viruses.

2) In a solution, hypochlorous acid and hypochlorite remain in an equilibrium.

At lower pH, hydrogen ions attack to hypochlorite ions to form hypochlorous acid.

At higher pH, hydrogen ions dissociate to form hypochlorite ions back thus maintaining the same equilibrium.

3)The pH of the human eyes and mucas membranes is around 7.4. Therefore water in a swimming pool cannot be kept at very high or low pH. It is maintained at 7.2 to 7.8 by adding acid or alkali.

4)If the pH is too high, muriatic acid is added to lower the pH.

If pH is too low, sodium carbonate is added to increase the pH till 7.2 to 7.8