A `5.25%` solution of a substance is isotonic with a `1.5%` solution of urea (molar mass `= 60g mol^(-1)`) in the same solvent. If the densities of both the solutions are assumed to be equal to `1.0 g cm^(-3)`, molar mass of the substance will be:

Options

A. `90.0 g mol^(-1)`
B. `115.0 g mol^(-1)`
C. `1050.0 g mol^(-1)`
D. `210.0 g mol^(-1)`

Answer

D

Explanation

Solutions with the same osmotic pressure are isotonic
Let the molar mass of the substances be M
`pi = C_(1)RT=C_(2)RT=pi_(2)`
So, `C_(1)=C_(2)`
As density of the solutions are same
So, `(5.25)/(M)=(15)/(60)rArr M =(5.25xx60)/(1.5)=210`