What is the vapor pressure at 23 ¢ªC of a solution of 1.20 g of naphthalene, C10H8, in 25.6 g of benzene, C6H6? The vapor pressure of pure benzene at 23 ¢ªC is 86.0 mmHg; the vapor pressure of naphthalene can be neglected. Calculate the vapor pressure lowering of the solution.

Answer 1

mols naphthalene = grams/molar mass
mols benzene = grams/molar mass
Xnaph = nnaph/total mols
Xbenzene = nbenzene/total mols
pbenzene = Xbenzene*P<sup>o_benzene

plowering = Xnaph*Po_benzene</sup>