# What is the pH of a 0.01 M solution of the strong acid HClO_4, perchloric acid?

May 11, 2016

$p H = - {\log}_{10} \left[{H}_{3} {O}^{+}\right] = - {\log}_{10} \left({10}^{-} 2\right) = 2$

#### Explanation:

This question may be answered without a calculator. We are asked to take the logarithm to the $\text{base 10}$ of ${10}^{- 2}$, which is clearly $- 2$, why? We are then asked to give the negative value of that logarithm.

Perchloric acid is exceptionally strong, and undergoes complete ionization in water:

$H C l {O}_{4} \left(a q\right) + {H}_{2} O \left(a q\right) \rightarrow {H}_{3} {O}^{+} + C l {O}_{4}^{-}$

Now not only do you have to learn how to take logarithms, you also have to learn how to take antilogarithms, if asked to find concentrations given a $p H$, see here .