Question

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:
A. `"210.0 g mol"^(-1)`
B. `"90.0 g mol"^(-1)`
C. `"115.0 g mol"^(-1)`
D. `"105 g mol"^(-1)`

Answer 1

Correct Answer - A
For isotonic solutions :
`pi_(1)=pi_(2)becausepi=CRT`
`C_(1)=C_(2)`
`(1.5//60)/(V)=(5.25//m)/(V)`
`:. m=210`]