Determine the freezing point (°C) of a 0.015 molal aqueous solution of MgSO₄. Assume i = 2.0 for MgSO₄. The molal freezing- point- depression constant of water is 1.86 °C/m. A) 0.000 B) - 0.056 C) - 0.028 D) - 0.084 E) - 0.17

Question

Quizplus · Accepted Answer

First, we need to use the van't Hoff factor (i) of 2.0 for MgSO4 to calculate the freezing point depression:

ΔTf = i * Kf * molality

where ΔTf = change in freezing point, Kf = molal freezing-point depression constant of water, and molality = moles of solute per kg of solvent.

Plugging in the values, we get:

ΔTf = 2.0 * 1.86 °C/m * 0.015 mol/kg = 0.056 °C

Since we're looking for the freezing point of the solution, we need to subtract this value from the freezing point of pure water, which is 0 °C. Therefore:

Freezing point = 0 °C - 0.056 °C = -0.056 °C

So the answer is B (-0.056).

Determine the Freezing Point (°C) of a 0