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. `90.0g" mol"^(-1)`
B. `115.0g" mol"^(-1)`
C. `105.0g" mol"^(-1)`
D. `210.0g" mol"^(-1)`

Answer

D

Explanation

Solution is is isotonic, `C_(1)RT=C_(2)RTrArrC_(1)=C_(2)`
Density of both the solutions are assumed to be equal to `1.0gcm^(-3)`
`5.25%` solution of a substance means 100g of solution contains 5.25g of solute and 1000 g of solution contains 52.5g of solute.
`"Hence," (52.5)/(M)=(15)/(60),`
M = molecular mass of the substance
`M=(52.5xx60)/(15)=210`