4.173 g of an organic compound (non-electrolyte) lowered the freezing point of 100.0 g of nitrobenzene by 2.6 °C. If the Kf of nitrobenzene is 8.1 °C∙ kg solvent/mol solute, the molecular mass of the non-electrolyte is ________.

Question

Quizplus · Accepted Answer

The molecular mass can be calculated using the formula ΔTf = (Kf * m), where m is the molality. Rearranging gives m = ΔTf / Kf. Substituting the given values, m = 2.6 / 8.1 = 0.321 mol/kg. The molality is moles of solute per kg of solvent, so moles of solute = 0.321 mol/kg * 0.1 kg = 0.0321 mol. The molecular mass is mass of solute / moles of solute = 4.173 g / 0.0321 mol = 130 g/mol.

4173 G of an Organic Compound (Non-Electrolyte) Lowered the Freezing