Final answer:
The 0.10 m AlCl₃ solution has the lowest vapor pressure among the choices because it dissociates into four particles per formula unit, which significantly lowers the vapor pressure according to Raoult's law. Option D is correct.
Step-by-step explanation:
The question asks which aqueous solution has the lowest vapor pressure. According to Raoult's law, the vapor pressure of a solution is lower than that of the pure solvent and is directly related to the mole fraction of the solvent in the solution.
When a solute is added to a solvent, it decreases the solvent's vapor pressure proportionally to the number of solute particles. For solutions with non-volatile solutes, the more particles a solute generates in solution, the greater the vapor pressure lowering.
Given the options:
0.10 m NaCl
0.10 m C₆H₁₂O₆
0.10 m AlCl₃
Sodium chloride (NaCl) dissociates into two particles per formula unit (Na⁺ and Cl⁻), whereas aluminum chloride (AlCl₃) dissociates into four particles per formula unit (Al³⁺ and three Cl⁻). Benzene (C₆H₁₂O₆), being an organic compound, does not dissociate in water.
Therefore, the solution with the lowest vapor pressure is 0.10 m AlCl₃, as it will produce the most particles when it dissociates, causing the greatest decrease in vapor pressure.