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?
A. `0.002%`
B. `0.004%`
C. `0.006%`
D. `0.008%`

7 views

1 Answers

Given density of formic acid =`1.15g//cm^(3)`
:.Weight of formic acid in `1` litre solution =`1.15xx10^(3)g`
thus `[HCOOH]=(1.15xx10^(3))/(46)=25M`
since in case of auto ionisation
`[HCOOH_(2)^(+)]=[HCOO^(-)]` and `[HCOO^(-)][HCOOH_(2)^(+)]=10^(-6)rArr [HCOO^(-)]=10^(-3)`
Now `%` dissociation of `HCOOH=([HCOO^(-)]xx100)/([HCOOH])=(10^(-3))/(25)xx100=0.004%`

7 views

Related Questions