An aqueous ethylene glycol solution being considered for use as a radiator coolant is 16.0% C₂H₆O₂ by weight. What would be the expected boiling point of this solution? For water, K_f is 1.86 °C m^-1 and K_b = 0.512 °C m^?1.Hint: convert percent by mass to molality, then find $\Delta$ T.

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Quizplus · Accepted Answer

To find the boiling point elevation, first convert the 16.0% by weight solution to molality. Assume 100 g of solution, which contains 16 g of ethylene glycol (C2H6O2) and 84 g of water. The molar mass of ethylene glycol is 62.07 g/mol, so there are 16 g / 62.07 g/mol = 0.258 mol of ethylene glycol. The mass of water is 84 g, which is 0.084 kg. The molality is 0.258 mol / 0.084 kg = 3.07 m. The boiling point elevation is ΔT = i * Kb * m = 1 * 0.512 °C/m * 3.07 m = 1.57°C. The normal boiling point of water is 100°C, so the boiling point of the solution is 100°C + 1.57°C = 101.57°C, approximately 101.6°C.

An Aqueous Ethylene Glycol Solution Being Considered for Use as a Radiator