A solution containing `10 g per dm^(3)` of urea (mol.wt. `= 60 g mol^(-1)`) is isotonic with a `5%` ( mass//vol.) of a non-volatile solute. The molecular mass of non-volatile solute 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 = 300 g mol^(-1)`.