A certain buffer solution contains equal concentartion of `X^(Theta)` and `HX`. The `K_(b)` for `X^(Theta)` is `10^(-10)`. The `pH` of the buffer is

Options

A. 4
B. 6
C. 7
D. 14

Answer

A

Explanation

`X^(-) +H_(2)O hArr OH^(-) +HX`
`K_(B) = ([OH^(-)][HX])/(X^(-))`
`HX hArr H^(+) +X^(-)`
`K_(a) = ([H^(+)][X^(-)])/([HX])`
`:. K_(a) xx K_(b) = [H^(+)] [OH^(-)]`
`=K_(a) = 10^(-14)`
Hence, `K_(a) = 10^(-4)`
Now, as `[X^(-)] = [HX], pH= pK_(a) = 4`