Naphthalene, C10H8, is used to make mothballs. Suppose you have a 0.0661m solution of Naphthalene in chloroform, CHCl3; calculate the new vapor pressure of the solution.

Question

Answer 1

Raoult's Law

P_soln = X_CHCl3 * P_o

P_soln = pressure of solution; X_CHCl3 = mol fraction of chloroform; P_o = vapor pressure of pure CHCl₃

Assume we have 1000 g of CHCl3

molar mass C10H8 = 130 g/mol

0.0661 m = 0.0661 mol C10H8 / 1000 g CHCl3

moles C8H10 = 0.0661 moles x 130 g/mol = 8.59 moles C8H10

moles CHCl3 = 1000 g x 1 mol/119 g = 8.40 moles CHCl3

Total moles = 8.59 + 8.40 = 17.0 moles

mole fraction CHCl3 = 8.40/17.0 = 0.494

P_soln = X_CHCl3 * P_o

P_soln = 0.494 * 156 mm Hg

P_soln = 77.1 mm Hg