Question

The vapor pressures of pure carbon disulfide and carbon tetrachloride are 360 and 99.8 torr, respectively, at 296 K. What is the vapor pressure of a solution containing 50.0 g of each compound

Answer 1

273.84 Torr

Given

Carbon disulfide = CS2

Carbon tetrachloride = CCL4

CS2 Partial Pressure = 360 Torr

CCL4 Partial Pressure = 99.8 Torr

Grams of CS2 and CCL4 = 50g each

Molar Mass of CS2 = 76.139 g/mol

Molar Mass of CCL4 = 153.82 g/mol

Calculating Moles of both substance...

The molar fraction is calculated by dividing the grams by the molar mass to get moles of each substance

Moles of CS2 = 50g/76.139g/mol

= 0.6567 mol

Moles of CCL4 = 50g/153.82g/mol

= 0.3251 mol

Total = 0.6567 + 0.3251 = 0.9818

Then, we find the Mole fraction of each substance.

Mole Fraction of CS2 = 0.6567/0.9818

= 0.6689

Mole fraction CCL4 = 0.3251/0.9818

= 0.3311

Vapour Pressure of Solution is calculated by

Mole fraction CS2 * Partial pressure CS2 +Mole fraction CCL4 * Partial pressure CCL4

Vapour Pressure = 0.6689 * 360 + 0.3311 * 99.8

= 240.80 + 33.04

= 273.84 Torr

= atm