Calculate the freezing point of a solution containing 20 grams of KCl and 2200.0 grams of water. The molal-freezing-point-depression constant (K_f)for water is 1.86 °C/m. A)-0.45 °C B)+0.45 °C C)-0.23 °C D)+0.23 °C E)1.23 °C

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Quizplus · Accepted Answer

The freezing point depression can be calculated using the formula ΔTf = i * Kf * m, where i is the van't Hoff factor for KCl (which is 2), Kf is 1.86 °C/m, and m is the molality of the solution. First, calculate the molality: moles of KCl = 20 g / 74.55 g/mol = 0.268 mol; molality = 0.268 mol / 2.2 kg = 0.122 m. Then, ΔTf = 2 * 1.86 °C/m * 0.122 m = 0.45 °C. The freezing point is lowered, so it is -0.45 °C.

Calculate the Freezing Point of a Solution Containing 20 Grams