Question

What is the pH of a pure WATER solution if the concentration of H+ in water is 10-7 ?

Answer 1

Given data:

Comcentration of H+ ion in water,

$\lbrack H^+\rbrack=10^{-7}\text{ }\frac{mol}{l}$

The pH value is given as,

$pH=-\log _{10}\lbrack H^+\rbrack_{}$

Substituting all known values,

$pH=-\log _{10}\lbrack10^{-7}\rbrack$

Since,

$\log _{10}(a^b)=b\times\log _{10}(a)$

Therefore,

$\begin{gathered} pH=-7\times(-\log _{10}\lbrack10\rbrack) \\ =7\log _{10}\lbrack10\rbrack \end{gathered}$

Since,

$\log _{10}\lbrack10\rbrack=1$

Therefore,

$\begin{gathered} pH=7\times1 \\ =7 \end{gathered}$

Therefore, pH of a pure water solution is 7.