What mass of ethanol,C₂H₅OH,should be added to 200.0 g of water in order to increase its boiling point to 102.5°C? The K_b for water is 0.512°C/m.Consider if the solute is an electrolyte or a nonelectrolyte.

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Quizplus · Accepted Answer

Ethanol is a nonelectrolyte, so it does not dissociate in solution. The boiling point elevation formula is ΔT = i * Kb * m, where i = 1 for nonelectrolytes. ΔT = 102.5°C - 100°C = 2.5°C. Rearranging the formula gives m = ΔT / Kb = 2.5°C / 0.512°C/m = 4.8828 m. The molality (m) is moles of solute per kg of solvent, so moles of ethanol = 4.8828 m * 0.2 kg = 0.97656 moles. The molar mass of ethanol is 46.08 g/mol, so mass = 0.97656 moles * 46.08 g/mol = 45 g.

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What Mass of Ethanol,C₂H₅OH,should Be Added to 200