If 1 mole of a non-volatile solute is dissolved in 1 kg of water, what is the ex

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Question: If 1 mole of a non-volatile solute is dissolved in 1 kg of water, what is the expected freezing point depression? (2019)

Options:

Correct Answer: 1.86 °C

Exam Year: 2019

Solution:

Freezing point depression (ΔTf) = i * Kf * m = 1 * 1.86 °C kg/mol * 1 mol/kg = 1.86 °C.

If 1 mole of a non-volatile solute is dissolved in 1 kg of water, what is the expected freezing point depression? (2019)

If 1 mole of a non-volatile solute is dissolved in 1 kg of water, what is the expected freezing point depression? (2019)

Step 1: Understand that freezing point depression (ΔTf) is a way to measure how much the freezing point of a solvent (like water) is lowered when a solute is added.
Step 2: Identify the formula for freezing point depression: ΔTf = i * Kf * m.
Step 3: Recognize that 'i' is the van 't Hoff factor, which is 1 for a non-volatile solute (it does not dissociate in solution).
Step 4: Identify Kf, the freezing point depression constant for water, which is 1.86 °C kg/mol.
Step 5: Determine 'm', the molality, which is 1 mole of solute per 1 kg of solvent (water), so m = 1 mol/kg.
Step 6: Plug the values into the formula: ΔTf = 1 * 1.86 °C kg/mol * 1 mol/kg.
Step 7: Calculate the result: ΔTf = 1.86 °C.

Freezing Point Depression – The decrease in the freezing point of a solvent when a solute is added, calculated using the formula ΔTf = i * Kf * m, where i is the van 't Hoff factor, Kf is the freezing point depression constant, and m is the molality of the solution.
Colligative Properties – Properties that depend on the number of solute particles in a solution rather than the identity of the solute.