Question

When the pH changes from $4$ to $2$, the hydrogen ion concentration will increase by a factor:

• A. $2$
• B. $1/2$
• C. ${10}^2$
• D. ${10}^{0.5}$

Answer 1

The correct option is C ${10}^2$

Formula:

$pH=-log\left[H^{+}\right]$

when $pH=4$

$\left[H^{+}\right]={10}^{-pH}={10}^{-4}$

when $pH=2$

$\left[H^{+}\right]={10}^{-pH}={10}^{-2}$

Increase in hydrogen ion concentration is ${10}^{-4}/{10}^{-2}=100$