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

• A. NaCl (sodium chloride, a strong electrolyte)
• B. K2SO4 (potassium sulfate, a strong electrolyte)
• C. CaCl2 (calcium chloride, a strong electrolyte)
• D. C6H12O6 (glucose, a non-electrolyte)

Answer: (D)

Verified step by step guidance

1. Understand that the vapor pressure of a solution is affected by the number of solute particles dissolved in the solvent, according to Raoult's Law. The more particles present, the greater the lowering of vapor pressure compared to pure solvent.
2. Identify that strong electrolytes dissociate into ions in solution, increasing the total number of solute particles, while non-electrolytes like glucose do not dissociate and remain as single molecules.
3. Calculate the van't Hoff factor (\(i\)) for each solute, which represents the number of particles the solute dissociates into: \\ \(i_{NaCl} = 2\), \(i_{K_2SO_4} = 3\), \(i_{CaCl_2} = 3\), and \(i_{C_6H_{12}O_6} = 1\).
4. Use the formula for the effective molality of particles in solution: \\ \(m_{effective} = i \times m\), where \(m\) is the molality of the solution. This helps compare how many particles each solute contributes to the solution.
5. Since vapor pressure lowering is proportional to the number of dissolved particles, the solution with the smallest \(m_{effective}\) (which is glucose, \(i=1\)) will have the highest vapor pressure among the given options.