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When 1 mol of HCl is added to 1 kg of water, the boiling point increases by 1.0 °C, but when 1 mol of acetic acid, CH₃CO₂H is added to 1 kg of water, the boiling point increases by only 0.5 °C. Explain.
9. Solutions
The Colligative Properties
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Which of the following compounds will have the highest boiling point?
A
0.10 M sucrose
B
0.10 M AgCl
C
0.25 M NH4NO3
D
0.45 M pure water
Verified step by step guidance1
Identify the colligative property that affects boiling point: Boiling point elevation is a colligative property, which means it depends on the number of solute particles in a solution, not their identity.
Determine the van't Hoff factor (i) for each compound: Sucrose is a non-electrolyte (i = 1), AgCl is a sparingly soluble salt (i = 2 for the ions Ag+ and Cl-), NH4NO3 is a strong electrolyte (i = 2 for the ions NH4+ and NO3-), and pure water has no solute particles (i = 0).
Calculate the effective concentration of particles for each solution: Multiply the molarity of each solution by its van't Hoff factor. For example, for NH4NO3, the effective concentration is 0.25 M * 2 = 0.50 M.
Compare the effective concentrations: The solution with the highest effective concentration of particles will have the highest boiling point due to the greatest boiling point elevation.
Conclude which compound has the highest boiling point: Based on the effective concentrations, determine that the solution with 0.25 M NH4NO3 has the highest boiling point because it has the highest effective concentration of solute particles.
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