Question

Vapour pressure of pure benzene and a solution with non electrolyte in benzene are 640 and 600 mm hg respectively. The molality of a solution

Answer 1

Answer:

The molality of a solution is 0.8547 molal.

Explanation:

The vapor pressure of the solution and mole-fraction of the solute are guiven by:

$\frac{p_o-p_s}{p_o}=\chi_2=\frac{n_2}{n_1+n_2}$

$p_o$ = Pressure of the benzene = 640 mmHg

$p_s$ = Pressure of the solution = 600mmhg

$\chi_2$ = Mole fraction of solute.

$\frac{640 mmHg-600 mmHg}{600 mmHg}=\frac{40 mmHg}{640 mmHg}=0.0625$

$\chi_2=0.0625=\frac{n_2}{n_1+n_2}$

we know that sum of all mole fraction is 1.

$n_2=0.0625 mol$

$\chi_1=1-0.0625=0.9375$

$n_1=0.9375 mol$

Mass of solvent =$0.9375 mol\times 78g/mol=73.125 g$

Molality of the solution =$\frac{0.0625 mol}{0.073125 kg}=0.8547 molal$

The molality of a solution is 0.8547 molal.

Answer 2

Answer:

opppos its correct year but it is 0..8