A mixture of `H_2C_2O_4` and `HCOOH` is heated with conc `H_2SO_4`. The gas produced is collected and on treatment with KOH solution, the volume of the gas decreases by `(1)/(6)` calculate the molar ratio of the two acids in the original mixture.

Explanation

Let x moles of formic acid and y moles of oxalic acid are heated.
`underset("x mol")(HCOOH) overset("Conc."H_(2)SO_(4)) to underset(x"mol")(H_(2)O + CO)`
`underset(COOH)overset(COOH)|overset("Conc".H_(2)SO_(4)) to underset(y"mol")(H_(2)O) + CO + underset("y mol")(CO_(2))`
Total moles of gaseous mixture = moles of CO + moles of `CO_(2)`
=x+y+y=x+2y
KOH absorbs only `CO_(2)` i.e. volume occupied by y moles. Under same conditions, ratios of volumes will be proportional to molar ratio of gases.
`("Moles of" CO_(2))/("Moles of both gases") = y/(x+2y) =1/6`
`6y= x+2y` or 4y =x
or `x/y =4`
`therefore` Ratio of HCOOH: `overset(COOH)underset(COOH)|= 4:1`