A pH of 5 is how many more times acidic than a pH of 6?

Sep 5, 2016

The $p H$ is logarithmic, and $p H = 5$ is $10 \times$ as acidic as $p H = 6$.
By definition, $p H = - {\log}_{10} \left[{H}_{3} {O}^{+}\right]$.
Thus when $p H$ $=$ $5$, $\left[{H}_{3} {O}^{+}\right] = {10}^{-} 5 \cdot m o l \cdot {L}^{-} 1$;
and when $p H$ $=$ $6$, $\left[{H}_{3} {O}^{+}\right] = {10}^{-} 6 \cdot m o l \cdot {L}^{-} 1$.
Thus there is there is a tenfold difference in acidity (and basicity) given $\Delta p H = 1$.