A 0.100 m solution of which one of the following solutes will have the lowest vapor pressure? Which will have have the highest vapor pressure?

A) KClO4 B) Ca (ClO4) 2 C) Al (ClO4) 3 D) Sucrose E) NaCl

The solution with Al (ClO₄) ₃ (option C) as solute will have the lowest vapor pressure.

The solution that has sucrose (option D) as solute will have the highest vapor pressure.

Explanation:

1) Raoult's law

Vapor pressure is a colligative property, which means that the vapor pressure of solutions is related to the amount of solute particles dissolved.

As Raoult's law states (you do not need the mathematical equation to solve this question), the decrease of the vapor pressure is proportional to the concentration of solute.

Since the concentrations of all the given solutions are the same, the solution that will have the lowest vapor pressure will depend on how each solute dissociates in the solution, while the solution with the least number of particles will have the highest vapor pressure.

2) Electrolytes

Electrolytes are substacnes that ionizes (dissociate into ions) in solution.

A) KClO₄ → K⁺ + ClO₄⁻ : each unit solute produces 2 ions B) Ca (ClO₄) ₂ → Ca²⁺ + 2ClO₄⁻: each unit of solute produces 3 ions C) Al (ClO₄) ₃ → Al⁺³ + 3ClO₄⁻: each unit of solute produces 4 ions D) Sucrose: this is a molecular compound, which does not dissociate E) NaCl → Na⁺ + Cl⁻ : each unit of solute produces 2 ions.

3) Conclusion

Since each Al (ClO₄) ₃ particle ionizes into more ions than the other solutes, the solution with it as solute will have the lowest vapor pressure; and the solution that has sucrose as solute (non-electrolyte) will have the highest vapor pressure.