Question

What is pH?

• A. $log{H}^{+}$
• B. $log\left[H^{+}\right]$
• C. $-log{H}^{+}$
• D. $-log\left[H^{+}\right]$

Answer 1

The correct option is D $-log\left[H^{+}\right]$

pH is a measure of the amount of activity of hydrogen ions (H+) in a solution and thus its acidic or basic nature can be determined. pH is described as “the negative of the logarithm of the molar hydronium-ion concentration". It has no unit but ranges from values 0-14.
$\text{pH = -log}{\text{[H}}^{+}]\text{or}-log[H_3{\text{O}}^{+}]$

For example, if the concentration of hydronium ions in a solution is $4.0\times {10}^{-8}\text{M}$, we can use the formula:
pH= $-log\left[H_3{\text{O}}^{+}\right]$
pH = $-log[4.0\times {10}^{-8}]$
pH = 7.40