Question

Vapour pressure of chloroform (CHCI) and
dichloromethane (CHCly) at 25°C are 200 mmHg
and 415 mmHg respectively. Vapour pressure of
the solution obtained by mixing 25.5 g of CHCl3
and 40g of CH2Cl, at the same temperature will
be: (Molecular mass of CHCl3 - 119.5 u and
molecular mass of CH,Cl, - 85 )
(1) 347.9 mmHg (2) 280.5 mmHg
(3) 173.9 mmHg (4) 615 mmHg​

Answer 1

Answer:

a

Explanation:

Molar mass of CH2Cl2 = 12 × 1 + 1 × 2 + 35.5 × 2 = 85 g mol–1

Molar mass of CHCl3 = 12 × 1 + 1 × 1 + 35.5 × 3 = 119.5 g mol-1

Moles of CH2Cl2= 40 g /85 g mol = 0.47 mol

Moles of CHCl3 = 25.5 g /119.5 g mol = 0.213 mol

Total number of moles = 0.47 + 0.213 = 0.683 mol

Molefraction of component 2

= 0.47 mol / 0.683 mol = 0.688

Molefraction of component 1

= 1.00 – 0.688 = 0.312

We know that

Ptotal = (p2-p1)*x

= 200 + (415 – 200) × 0.688

= 200 + 147.9

= 347.9 mm Hg