If 1 mole of a non-electrolyte solute is dissolved in 1 kg of water, what is the
Practice Questions
Q1
If 1 mole of a non-electrolyte solute is dissolved in 1 kg of water, what is the expected change in freezing point?
0.0 °C
-1.86 °C
-3.72 °C
-5.58 °C
Questions & Step-by-Step Solutions
If 1 mole of a non-electrolyte solute is dissolved in 1 kg of water, what is the expected change in freezing point?
Correct Answer: -1.86 °C
Step 1: Understand that when a solute is dissolved in a solvent (like water), it can change the freezing point of the solvent.
Step 2: Know that the freezing point depression is a property that tells us how much the freezing point will lower when a solute is added.
Step 3: For water, the formula to calculate the freezing point depression is: ΔTf = i * Kf * m, where ΔTf is the change in freezing point, i is the van 't Hoff factor (which is 1 for non-electrolytes), Kf is the freezing point depression constant for water (1.86 °C kg/mol), and m is the molality of the solution.
Step 4: Since we have 1 mole of solute in 1 kg of water, the molality (m) is 1 mol/kg.
Step 5: Plug the values into the formula: ΔTf = 1 * 1.86 °C kg/mol * 1 mol/kg.
Step 6: Calculate the result: ΔTf = 1.86 °C.
Step 7: Since the freezing point decreases, we express this as -1.86 °C.
Freezing Point Depression – The phenomenon where the freezing point of a solvent decreases 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.
Non-Electrolyte Solute – A solute that does not dissociate into ions in solution, affecting colligative properties like freezing point depression based solely on the number of solute particles.
