Given value, Solution of urea =10% Solution of non-volatile solute ' x′=6% ∵ Isotonic solution has the same osmotic pressure and hence the same concentration in the solution. We know that, osmotic pressure (π)=CRT here, R and T are constant ∵π1=π2 ∴C1RT1=C2RT2 10% solution of urea =6% of solution of ' x′
10
100×60
=
6
100×x
(Molecular weight of urea=60 ) x=6×6=36gmol−1 Hence, the atomic mass of solute ' x′ is 36gmol−1.