Question

After you preform your experiment, you determine that the kf value for naphthalene is 6.91 °c/m . you are using 10g of naphthalene and added 1.0 g of your unknown. the the freezing point of the solvent decreased by 4.47 °c when the unknown was added. knowing this information, determine the molar mass of the unknown. g/mol

Answer 1

Answer is: molar mass of compound is 154,58 g/mol.
m(naphthalene) = 10 g = 0,01 kg.
m(unknown compound) = 1,00 g.
ΔT (solution) = 4,47 °C.
Kf(naphthalene) = 6,91°C/m; cryoscopic constant.
M(unknown compound) = Kf(naphthalene)· m(unknown compound) ÷ m(naphthalene) · ΔT(solution).
M(xylene) = 6,91°C/m · 1 g ÷ 0,01 kg · 4,47°C.
M(xylene) = 154,58 g/mol.