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Choose the aqueous solution below with the highest freezing point. These are all solutions of nonvolatile solutes and you should assume ideal van't Hoff factors where applicable.
These all have the same freezing point.
0.200 m Ba(NO3)2
0.200 m Mg(ClO4)2
0.200 m Na3PO3
0.200 m HOCH2CH2OH

Respuesta :

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Answer:

  • HOCH₂CH₂OH

Explanation:

The decrease of the freezing point is a colligative property, which means that it depends on the number of particles dissolved (solute particles).

The equation for the decrease of the freezing point is:

  • ΔTf = m × Kf × i

Where:

  • ΔTf is the decrease of the freezing point
  • m is the molality of the solution
  • Kf is the molal freezing constant, which depends on the solvent
  • i is the van't Hoff factor.

For all the given solutions the molality and Kf are the same. So, the difference is given by the van't Hoff factor.

The ideal van't Hoff factor is assumed to be equal to the number of ions into which a solute dissociates in solutions (for ionic solutes) and equal to 1 for covalent molecules.

Then, you must just need to use the dissociation equation for each solute:

  • Ba(NO₃)₂ → Ba⁺² + 2NO₃⁻ ⇒ i = 3

  • Mg(ClO₄)₂ → Mg²⁺ + 2 ClO₄⁻ ⇒ i = 3

  • Na₃PO₃ → 3Na⁺ + PO₃³⁻ ⇒ i = 4

  • HOCH₂CH₂OH is a covalent molecule ⇒ i = 1

Hence, the solution that will experience the lowest freezing point reduction is HOCH₂CH₂OH because it has the lowest van't Hoff factor, and that will be the solution with the highest freezing point.

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