Question

When 7.94 g of xylene was added to 132.5 g of cyclohexane, the freezing point of the solution was -4.9oC. What is the molar mass of xylene?

Answer 1

Answer is: molar mass of xylene 106,18 g/mol.
m(xylene) = 7,94 g.
m(cyclohexane) = 132,5 g.
T (solution) = - 4,9 °C.
Tf(cyclohexane) = 6,5 °C, frezing point.
Kf(cyclohexane) = 20,2 K·kg/mol; cryoscopic constant.
ΔT(solution) = 6,5°C - (-4,9°C) = 11,4°C = 11,4 K.
M(xylene) = Kf · m(xylene) ÷ m(cyclohexane) · ΔT(solution).
M(xylene) = 20,2 K·kg/mol · 7,94 g ÷ 0,1325 kg · 11,4 K.
M(xylene) = 106,18 g/mol.