Question

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

Answer 1

Correct Answer - B
`pi_(1)` (urea) = `pi_(2)` (unknown solute)
`C_(1)` (urea) = `C_(2)` (unknown solute)
`[(w_(B)xx1000)/(m_(B)xxV)]_("urea")=[(w_(B)xx1000)/(m_(B)xxV)]_("unknown solute")`
`(10xx1000)/(60xx1000)=(5xx1000)/(m_(B)xx100)`
`m_(B)=300 "g mol"^(-1)`]