The self ionisation constant for pure formic acid `K=[HCOOH_(2)^(+)][HCOO^(-)]` has been estimated as `10^(-6)` at room temperature .The density of formic acid is `1.15g//cm^(3)` .What percentage of formic acid molecules in pure fomic acid are converted to formation ion?

Explanation

Wt. of formic acid in 1L solution
`=1.22xx1000=1.22xx10^3` g
[HCOOH]=`(1.22xx10^3)/46`=26.5 M
Since in case of auto ionisation ,
`[HCOOH_2^+]=[HCOO^-]`
`[HCOOH_2^+][HCOO^-]=10^(-6)`
`therefore [HCOO^-]=10^(-3)`
`therefore` % Dissociation of HCOOH =`([HCOO^-])/([HCOOH])xx100`
`=10^(-3)/26.5 xx100` =0.004%