A solution containing`8.6` urea in one litre was found to be isotonic with a `5%`(wt./vot.)solution of an organic non-volatile solute. The molecular weight of latter is:

Explanation

Solution are isotonic
so `pi_(1) = pi_(2)`
`(n_(1))/(V_(1)) ST =(n_(2))/(V_(2)) ST {S & T` are constant}
so, `(n_(1))/(V_(1)) = (n_(2))/(V_(2))`
or `((w_(1))/(m_(1)xxv_(1)))_(urea) = ((w_(2))/(m_(2)xxv_(2)))_("organic")`
or `(8.6)/(60 xx 1000) = (0.5)/(m_(2) xx 100)`
`m_(2) = 34.89 gm//mol`