Question

What is the concentration of hydronium ions in a solution that has a pH of -3? Why is such a solution impossible to prepare?

Answer 1

Both of these questions can be answered by one calculation - the `["H"_3"O"^+]` for this pH.

Explanation:

Negative pH values correspond to very high levels of `"H"_3"O"^+` concentration.

Mathematically, the relation is

`["H"_3"O"^+]=10^(-"pH")`

If the pH is negative, the expression becomes

`["H"_3"O"^+]=10^(-(-3))= 10^3="1000 mol/L"`

In answer to your second question, it is not possible to add sufficient solute to a solution to reach a concentration of `"1000 mol/L"`! Even in the case of a low-mass strong acid like `"HCl"`, this would require `"36500 g"` dissolved in only one litre of solution!