Question

QUESTION 10

A solution is prepared by dissolving 40.0 g of sucrose (C₁₂H₂₂O₁₁, MM = 342 g/mol) in 250. g of H₂O at 298 K. What is the vapor pressure of the solution if the vapor pressure of water at 298 K is 23.76 mm Hg?

		0.198 mm Hg
		20.5 mm Hg
		23.6 mm Hg
		28.0 mm Hg

Answer 1

Molar mass of H2O,

MM = 2*MM(H) + 1*MM(O)

= 2*1.008 + 1*16.0

= 18.016 g/mol

Molar mass of C12H22O11 = 342 g/mol

n(H2O) = mass/molar mass

= 250.0/18.016

= 13.8766

n(C12H22O11) = mass/molar mass

= 40.0/342

= 0.1169

n(H2O),n1 = 13.8766 mol

n(C12H22O11),n2 = 0.1169 mol

Total number of mol = n1+n2

= 13.8766 + 0.1169

= 13.9934 mol

Mole fraction of each components are

X(H2O) = n1/total mol

= 13.8766/13.9934

= 0.9916

According to Raoult’s law:

P = Po*X(solvent)

p = 23.76*0.9916

p = 23.6 mmHg

Answer: 23.6 mmHg