A solution contains naphthalene (C10H8) dissolved in hexane (C6H14) at a concentration of 11.39{\rm \\%} naphthalene by mass. Calculate the vapor pressure at 25 ∘C of hexane above the solution. The vapor pressure of pure hexane at 25 ∘C is 151 torr.

Answer 1

11.39% w/w is 11.39g naph/100 g solution.
100 g soln = 11.30g naph + 88.61g hexane.
n = mols naph = nnaph = grams/molar mass
nhexane = grams/molar mass.
Take sum of mols =
ntotal = nnaph + nhexane.

Xhex = nhexane/total mols

psolution = X_hexane*P^o_hexane</sub

Answer 2

p_soln = X_hexane*P^o_hexane