What is the molar mass of toluene if 0.85 g of toluene depresses the freezing point of 100. g of benzene by 0.47°C? (K_f of benzene is 5.12°C/m.) A) 93 g/mol B) 78 g/mol C) 10.7 g/mol D) 82 g/mol E) 927 g/mol

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Quizplus · Accepted Answer

The molar mass of toluene can be calculated using the formula ΔTf = Kf * m, where ΔTf is the depression in freezing point, Kf is the cryoscopic constant of benzene, and m is the molality of the solution. Given ΔTf = 0.47°C and Kf = 5.12°C/m, we first find the molality: m = ΔTf / Kf = 0.47 / 5.12 = 0.0918 mol/kg. Since 0.85 g of toluene causes this depression in 100 g (0.1 kg) of benzene, the number of moles of toluene is 0.0918 mol/kg * 0.1 kg = 0.00918 mol. The molar mass of toluene is then 0.85 g / 0.00918 mol = 92.59 g/mol, which rounds to 93 g/mol.

What Is the Molar Mass of Toluene If 0