What is `[H^(+)]` is mol/ L of a solution that is 0.20 M in `CH_(3)CO ON a` and 0.10 M in `CH_(3)CO OH` ? `K_(a)` for `CH_(3)CO OH=1.8xx10^(-5)`

Options

A. `3.5xx10^(-4)`
B. `1.1xx10^(-5)`
C. `1.8xx10^(-5)`
D. `9.0xx10^(-6)`

Answer

D

Explanation

`pH=p K_(a)+log [("Salt")/("Acid")]`
`log[H^(+)]=log K_(a)-log [("Salt")/("Acid")]`
`log [H^(+)]=log K_(a)+log [("Acid")/("Salt")]`
`[H^(+)]=K_(a)[("Acid")/("Salt")]`
`=1.8xx10^(-5)xx(0.1)/(0.2)=9xx10^(-6)`