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{ }(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*\log _(10)(a)`

Therefore,

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

Since,

`\log _(10)\lbrack10\rbrack=1`

Therefore,

`\begin{gathered} pH=7*1 \\ =7 \end{gathered}`

Therefore, pH of a pure water solution is 7.