A 4% solution of sucrose is isotonic with 3% solution of an unknown organic substance. Calculate the molecular mass of unknown resistance.

Answer:

AS both the solution are  isotonic they should have same concentrationin mole/litre
for sucrose solution concentration =4g/100cm³
                                                   = 40g/Litre

molar mass of sucrose C ₁₂H₂₂O₁₁ = 342
        therefore we get =40/342 moles/litre

For unknown substance Let N be the molecular mass then concentration = 3g/100cm³ 
                                    = 30g/Litre

                                   = 30/N moles/Litre
comparing the both equation
30/N = 40/342

N=(30 x 342)/40

N= 256.5
Molecular mass of oragnic compound