Question

What is the relative lowering of vapour pressure of 26% solution of a non volatile solute molecules weight 52 in diethyl ether

Answer 1

Answer : The relative lowering of vapor pressure of solution is, 0.37

Solution :

As the relative lowering of vapor pressure is directly proportional to the amount of dissolved solute.

26% solution of a non-volatile solute means that 26 grams of non-volatile solute present in 100 grams of diethyl ether.

The formula for relative lowering of vapor pressure will be,

$\frac{\Delta p}{p^o}=X_2$

or,

$\frac{\Delta p}{p^o}=\frac{w_2M_1}{w_1M_2}$

where,

$p^o$ = vapor pressure of pure solvent

$\Delta p$ = change in vapor pressure

$X_2$ = mole fraction of non-volatile solute

$w_2$ = mass of non-volatile solute  = 26 g

$w_1$ = mass of solvent  (diethyl ether) = 100 g

$M_1$ = molar mass of solvent (diethyl ether) = 74 g/mole

$M_2$ = molar mass of non-volatile solute = 52 g/mole

Now put all the given values in this formula ,we get :

$\frac{\Delta p}{p^o}=\frac{26\times 74}{100\times 52}$

$\frac{\Delta p}{p^o}=0.37$

Therefore, the relative lowering of vapor pressure of solution is, 0.37