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

Jan 3, 2017

Both of these questions can be answered by one calculation - the $\left[{\text{H"_3"O}}^{+}\right]$ for this pH.

#### Explanation:

Negative pH values correspond to very high levels of ${\text{H"_3"O}}^{+}$ concentration.

Mathematically, the relation is

$\left[\text{H"_3"O"^+]=10^(-"pH}\right)$

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 $\text{1000 mol/L}$! Even in the case of a low-mass strong acid like $\text{HCl}$, this would require $\text{36500 g}$ dissolved in only one litre of solution!