Question

A solution containing 10 gram per decimeter cube of urea is isotonic with 5% solution of non volatile solute the molecular mass of this non volatile solute is

Answer 1

Answer : The molecular mass of this non volatile solute is, 300 g/mole

Explanation :

10 gram per decimeter cube of urea is isotonic with 5% solution of a non-volatile solute. That means, between these solutions osmosis is not possible so their molar concentrations are equal to each other.

Isotonic solutions are those solutions which have the same osmotic pressure.

Formula used :

$\pi =CRT$ if osmotic pressures are equal at the same temperature, concentrations must also be equal.

$\pi$ = osmotic pressure

C = concentration

R = solution constant

T = temperature

For urea solution : 10 g of urea is dissolved in 1000 ml of solution.

For non-volatile solute : 5 g of non-volatile solute is dissolved in 100 ml of solution.

$\pi_{urea}=\pi_{\text{non-volatile}}$

or,

$C_{urea}=C_ {\text{non-volatile}}$

$\frac{\text{Mass of urea}\times 1000}{\text{Molar mass of urea}\times \text{volume of solution in ml}}=\frac{\text{Mass of non-volatile solute}\times 1000}{\text{Molar mass of non-volatile solute}\times \text{volume of solution in ml}}$

Now put all the given values in this expression, we get

$\frac{10g\times 1000}{60g/mole\times 1000ml}=\frac{5g\times 1000}{M_{\text{non-volatile}}\times 100ml}$

$M_{\text{non-volatile}}=300g/mole$

Therefore, the molecular mass of this non volatile solute is, 300 g/mole

Answer 2

Answer :-

________ 300g/ mol^-1 _______