Calculate the freezing point of a solution containing 5.0 grams of KCl and 550.0 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 is calculated using 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 = 5.0 g / 74.55 g/mol = 0.067 moles; molality = 0.067 moles / 0.550 kg = 0.122 m. Then, ΔTf = 2 * 1.86°C/m * 0.122 m = 0.45°C. The freezing point is lowered, so it's -0.45°C.

Calculate the Freezing Point of a Solution Containing 5