Question

Which of the following solutions will have the lowest freezing point?

O 0.015 mol kg-1 CaI₂
O 0.010 mol kg-1 NH₄Cl
O 0.010 mol kg-1 K₂SO₄
O 0.035 mol kg-1 C₄H₉OH

Answer 1

The solution with 0.015 mol kg^-1 CaI2 will have the lowest freezing point since it has both a higher molality and produces 3 particles per formula unit, resulting in a greater number of particles in solution compared to the other options. The correct answer is O 0.015 mol kg-1 CaI₂.

Step-by-step explanation:

The freezing points of solutions are affected by the number of solute particles present in the solution. According to the concept of colligative properties, the freezing point of a solution decreases with the increasing concentration of solute particles.

To determine which solution will have the lowest freezing point, we need to consider both the molality of the solutions and the number of particles each solute produces when dissolved.

For the given solutions:

• 0.015 mol kg-1 CaI2 will produce 3 particles per formula unit (1 Ca2+ and 2 I-).
• 0.010 mol kg-1 NH4Cl will produce 2 particles per formula unit (1 NH4+ and 1 Cl-).
• 0.010 mol kg-1 K2SO4 will produce 3 particles per formula unit (2 K+ and 1 SO42-).
• 0.035 mol kg-1 C4H9OH (butanol) is a non-electrolyte and will produce 1 particle per formula unit.

Comparing these, CaI2 and K2SO4 both produce 3 particles per formula unit, but since CaI2 has a higher molality (0.015 mol kg-1) compared to K2SO4 (0.010 mol kg-1), the solution of CaI2 will have the lowest freezing point.