Multiple Choice
Which of the following will increase the vapor pressure of a liquid according to Raoult's Law?
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14. Solutions
Vapor Pressure Lowering (Raoult's Law)
Multiple Choice
Which of the following aqueous solutions would have the highest vapor pressure?
A
0.10 M C6H12O6 (glucose)
B
0.10 M CaCl2
C
0.10 M NaCl
D
0.10 M AlCl3
Verified step by step guidance1
Recall that vapor pressure lowering in a solution is a colligative property, which depends on the number of solute particles dissolved in the solvent, not their identity.
Calculate the van't Hoff factor (i) for each solute, which represents the number of particles the solute dissociates into in solution: for glucose (C6H12O6), i = 1 (no dissociation); for NaCl, i = 2; for CaCl2, i = 3; for AlCl3, i = 4.
Determine the effective concentration of particles in each solution by multiplying the molarity by the van't Hoff factor: effective concentration = i × molarity.
Understand that the solution with the highest effective concentration of solute particles will have the greatest vapor pressure lowering, and thus the lowest vapor pressure.
Conclude that the solution with the lowest effective concentration of solute particles will have the highest vapor pressure; therefore, compare the values to identify which solution has the highest vapor pressure.
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