What is the freezing point depression of a solution containing 3 moles of KCl in

Practice Questions

Q1
What is the freezing point depression of a solution containing 3 moles of KCl in 1 kg of water? (Kf for water = 1.86 °C kg/mol) (2022)
  1. 5.58 °C
  2. 3.72 °C
  3. 1.86 °C
  4. 7.44 °C

Questions & Step-by-Step Solutions

What is the freezing point depression of a solution containing 3 moles of KCl in 1 kg of water? (Kf for water = 1.86 °C kg/mol) (2022)
  • Step 1: Identify the formula for freezing point depression, which is ΔTf = i * Kf * m.
  • Step 2: Determine the van 't Hoff factor (i) for KCl. Since KCl dissociates into K+ and Cl-, i = 2.
  • Step 3: Find the Kf value for water, which is given as 1.86 °C kg/mol.
  • Step 4: Calculate the molality (m) of the solution. Since there are 3 moles of KCl in 1 kg of water, m = 3 moles/kg.
  • Step 5: Substitute the values into the formula: ΔTf = 2 * 1.86 °C kg/mol * 3 m.
  • Step 6: Perform the multiplication: ΔTf = 2 * 1.86 * 3 = 11.16 °C.
  • Step 7: The freezing point of the solution is lowered by 11.16 °C.
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