Question

Calculate the pKa of hypochlorous acid (HClO, a weak acid). A 0.015 M solution of hypochlorous acid has a pH of 4.64.

Answer 1

"7.46" is the correct answer.

Step-by-step explanation:

Given that:

`pH=4.64`

`C=0.015 \ M`

The equation:

⇒
`HA \rightleftharpoons H^++A^-`

HA = C - Cα

H⁺ = Cα

A⁻ = Cα

now,

⇒
`pH=-log(H^+)`

`=-log(C \alpha)`

`=4.64`

`C \alpha = 2.3* 10^-5 \ M`

As we know,

⇒
`K_a=C \alpha^2`

`=((C \alpha)/(C) )^2* C`

`=((2.3* 10^(-5))^2)/(0.015)`

`=3.5* 10^(-8)`

hence,

⇒
`pK_a=-log(K_a)`

`=7.46`