Question

At 25°C, the [$H^{+}$] of an acidic solution is $10^{-5}$. Find out its pH.

Answer 1

Given, at 25°C the concentration of $\left[ { H }^{ + } \right] is { 10 }^{ -5 }$ in acidic solution

We know that,

At room temperature,

${ K }_{ w }\quad =\quad \left[ { H }^{ + } \right] \left[ { OH }^{ - } \right] \quad =\quad { 10 }^{ (-14) }$

It is given that, $\left[ { H }^{ + } \right] \quad =\quad { 10 }^{ -5 }$, hence $\left[ { OH }^{ - } \right] \quad =\quad { 10 }^{ -9 }$

So, $pOH\quad =\quad -log\left[ { OH }^{ - } \right] \quad =\quad 9$

But, $pH + pOH = 14$

So, pH of the solution is 9.