The pH of solution obtained by mixing equal volumes of two aqueous solutions of pH 5 and pH 3 of the same substance is :

Options

A. `3.5`
B. `4.5`
C. `3.3`
D. 4

Answer

C

Explanation

Let 100 ml of both the solutions are mixed
`[H^(+)]` in solution of pH = 5 is `10^(-5)`
`[H^(+)]` in solution of pH = 3 is `10^(-3)`
Total `[H^(+)]=10^(-5)+10^(-3)`
`=1.01xx10^(-3)`
Total volume = 2000 ml
Conc. in mixture
`=(1.01xx10^(-3)xx1000)/(2000)=5.05xx10^(-4)`
`pH=-log(5.05xx10^(-4))=3.3`