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Multiple Choice
What is the freezing point depression of a 0.050 m FeCl3 solution at 25.0°C, assuming complete dissociation and using a Kf value of 1.86°C kg/mol for water?
A
0.09°C
B
0.28°C
C
0.37°C
D
0.14°C
Verified step by step guidance
1
Identify the formula for freezing point depression: ΔT_f = i * K_f * m, where ΔT_f is the freezing point depression, i is the van't Hoff factor, K_f is the cryoscopic constant, and m is the molality of the solution.
Determine the van't Hoff factor (i) for FeCl3. Since FeCl3 dissociates into one Fe^3+ ion and three Cl^- ions, i = 1 + 3 = 4.
Use the given values: K_f = 1.86°C kg/mol and m = 0.050 m. Substitute these values into the formula: ΔT_f = 4 * 1.86°C kg/mol * 0.050 m.
Calculate the product of the van't Hoff factor, the cryoscopic constant, and the molality to find the freezing point depression.
Interpret the result: The calculated ΔT_f will give you the decrease in the freezing point of the solution compared to pure water.