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The ionisation cosntabnt of an acid, K(a...

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 ?

A

Acetic acid `gt` hypochlorous acid `gt` formic acid

B

Hypochlorous acid `gt` acetic acid `gt` formic acid

C

Formic acid `gt` hypochlorous acid ` gt` acetic acid

D

Formic acid `gt` acetic acid `gt` hypochlorous acid

Text Solution

Verified by Experts

The correct Answer is:
D
As the acidity or`K_(a)` value increase , pH decreases , thus the order of pH value of the acids is
`underset ((3.8 xx10^(-8)))("Hypochlorous acid") lt underset ((1.74 xx 10^(-5))) "Acetic acid "lt underset ((1.8 xx 10^(4))) " Formic acid "`
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