The ionisation cosntabnt of an acid, `K_(a)` is the meaure of strength of an acid. The `K_(a)` values of acetic acid, hypochlorous acid and formic acid are `1.74xx10^(-5)`, `3.0xx10^(-8)` and `1.8xx10^(-4)` respectively. Which of the following orders of ph of `0.1` mol `dm^(-3)` solutions of these acids is correct ?

Options

A. acetic acid gt hypochlorous acid gt formic acid
B. hypochlorous acid gt acetic acid gt formic acid
C. formic gt hypochlorous acid gt acetic acid
D. formic acid gt acetic acid gt hypochlorous acid

Answer

B

Explanation

We know that
`[H^(+)]=sqrt(K_(a)xxc)`
and `ph ="log"(1)/([H^(+)]`
This means that greater the `K_(a)`, stronger is t he acid and lesser is the ph of the solution. Therefore, (b) is the correct order of decreasing ph values.