Question

a. Calculate the mole fraction (x) of biphenyl (MW 154.21 g/mol) dissolved in naphthalene (MW = 128.17 g/mol) for a 0.250 m solution. Calculate the %mass biphenyl in the solution from part a.

Answer 1

Molarity = moles of solvent/mass of solvent (kg) = 0.25 m let mass of solvent = 1 kg therefore moles of solvent = 0.25 moles mass of naphthalene = 100 degree g Molar mass = 128.17 g/mol therefore moles of naphthalene = 100 g/128.17 g/mol = 7.802 mol Mole fraction of biphenye = moles of biphenye/total moles x = 0.25/0.25 + 7.802 x = 0.031 Solute Moles of biphenye = 0.25 moles Molar mass = 154.21 g/mol therefore mass = 154.21 times 0.25 = 38.55 g Mass of solution = mass of solute + mass of solute = 38.55 + 1000 = 1038.55g mass percent of biphenye = mass of bipheye/total mass of solution = 38.55/1038.55 times 100% = 3.71 %