Question

How do you determine the pH of a solution that has a hydroxide concentration of `9.3*10^-16` M? Is this solution acidic or basic?

Answer 1

You can determine it like this:

Explanation:

Assuming we have aqueous conditions, water dissociates:

`H_2O_((l))rightleftharpoonsH_((aq))^(+)+OH_((aq))^(-)`

`K_(w)=[H_((aq))^(+)][OH_((aq))^(-)]=10^(-14)"mol"^2."l"^(-2)` at `25^@"C"`

This means that `[OH_((aq))^(-)]=10^(-7)"mol/l"` from the ionisation of water.

An `OH_((aq))^(-)` concentration of `9.3xx10^(-16)"mol/l"` is vanishingly small in comparison so I would say that the solution is neither acid or alkali but neutral.