Question

It was mentioned that you should not expect the pH of distilled water to be 7.00 as ordinarily measured in the laboratory. What component(s) of the atmosphere might cause distilled water in the laboratory to have pH < 7.0? Write an equation to show this.

Answer 1

Carbon dioxide

Step-by-step explanation:

laboratory to have a pH of less than 7.0.

Carbon (IV) oxide in the atmosphere is capable of dissolving into the distilled water to form a weak acid. Any pH that is less than 7.0 is acidic while any pH above 7.0 is alkaline or basic.

First, the carbon (IV) oxide enters the water through an equilibrium with the atmosphere:

`CO_2 (aq) <--> CO_2 (g)`

Thereafter, aqueous carbon (IV) oxide can then react with water to form a weak carbonic acid:

`CO_2 (aq) + H_2O --> H_2CO_3 (aq)`