A solution containing 10 g per `dm^(3)` of urea (molecular mass = 60 g `mol^(–1)`) is isotonic with a 5% solution of a nonvolatile solute. The molecular mass of this nonvolatile solution is:

Options

A. `300 g mol^(-1)`
B. `350 g mol^(-1)`
C. `200 g mol^(-1)`
D. `250 g mol^(-1)`

Answer

A

Explanation

Suppose, the molecular mass of non-volatile solute is M
Molar conc. of urea solution `=(10)/(60)` per `dm^(3)`
Molar conc. of non-volatile solute solution
`=(5)/(M)` per 100 mL.
`=(50)/(M)` per `dm^(3)`
For isotonic solution at the same temperature molar concentration are equal
`(10)/(60)=(50)/(M)`
or `M=300gmol^(-1)`.