Question

The pH of the solution is 2. If its pH is to be raised to 4 then the $\left[H^{+}\right]$ of the original solution has to be:

• A. doubled
• B. halved
• C. increased by 100 times
• D. decreased by 100 times

Answer 1

The correct option is D decreased by 100 times

Change in pH is $\Delta pH=p{H}_2-p{H}_1=4-2=2$.
Thus ratio of hydrogen ion concentration is $\frac{[H{]}_2^{+}}{[H{]}_1^{+}}={10}^{-2}=0.01$.
Hence, the hydrogen ion concentration should be decreased by 100 times.