A mono basic weak acid solution has a molarity of 0.005 and pH of 5. What is its percentage ionisation in this solutino ?gt

Options

A. `2.0`
B. `0.2`
C. `0.5`
D. `0.25`

Answer

B

Explanation

`HA rarr H^(+) + A^(-)`
`K_(a) = ([H^(+)][A^(-)])/([HA]) , pH = -log[H^(+)]`
`[H^(+)] = 10^(-5) , [H^(+)] = [A^(-)]`
`K_(a) = (10^(-5) xx 10^(-5))/(0.005) = 2 xx 10^(-8)`
`alpha = sqrt((K_(a))/(C)) = 2 xx 10^(-3)`
Percentage ionization = 0.2