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Multiple Choice
What is the freezing point, in °C, of a solution made with 1.15 mol of CHCl₃ in 530.0 g of CCl₄ (Kf = 29.8 °C/m, normal freezing point, Tf = -22.9 °C)?
A
-35.0 °C
B
-45.7 °C
C
-22.9 °C
D
-56.2 °C
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Verified step by step guidance
1
First, identify the formula for freezing point depression: ΔTf = Kf × m, where ΔTf is the change in freezing point, Kf is the cryoscopic constant, and m is the molality of the solution.
Calculate the molality (m) of the solution using the formula: m = moles of solute / kilograms of solvent. Here, the solute is CHCl₃ and the solvent is CCl₄.
Convert the mass of the solvent (CCl₄) from grams to kilograms: 530.0 g = 0.530 kg.
Calculate the molality: m = 1.15 mol / 0.530 kg.
Use the freezing point depression formula to find the change in freezing point: ΔTf = 29.8 °C/m × m. Then, subtract ΔTf from the normal freezing point of CCl₄ (-22.9 °C) to find the new freezing point of the solution.