Question

Biphenyl, C12H10, is a nonvolatile, nonionizing solute that is soluble in benzene, C6H6. At 25 °C, the vapor pressure of pure benzene is 100.84 torr. What is the vapor pressure of a solution made from dissolving 16.0 g of biphenyl in 25.9 g of benzene?

Answer 1

Apply

dP = xsolute * P°solvent

P°solvent = 100.84 torr

x solute = mol of solute / (total mol)

MW of bipheyl =154.21  

mol of solute = mass/MW = 16.0/154.21 = 0.103754 mol of bipheyl

MW of benzene= 78.11

mol benzne = mass/MW = 25.9/78.11 = 0.331583 mol of benzene

then

total mol = 0.103754 +0.331583 = 0.435337

x solute = 0.103754 /0.435337 = 0.23833

then

dP = xsolute * P°solvent = 0.23833*100.84 = 24.0331972

Pmix = Psolvent - d P = 100.84-24.0331972 = 76.806 torr