Multiple Choice
What is the boiling point of a solution that contains 50.0 g of FeBr3 in 200.0 g of water, given that the boiling point elevation constant (Kb) for water is 0.512 °C/m?
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14. Solutions
Boiling Point Elevation
Multiple Choice
Which of the following solutions will have the highest boiling point elevation when dissolved in water?
A
Pb(NO3)2
B
KMnO4
C
C2H5OH
D
NaCl
Verified step by step guidance1
Identify the concept of boiling point elevation, which is a colligative property. It depends on the number of solute particles in a solution, not their identity.
Determine the van't Hoff factor (i) for each compound, which represents the number of particles the compound dissociates into in solution. For example, NaCl dissociates into Na+ and Cl-, so i = 2.
Calculate the van't Hoff factor for each compound: Pb(NO3)2 dissociates into 3 ions (Pb2+ and 2 NO3-), KMnO4 dissociates into 2 ions (K+ and MnO4-), C2H5OH does not dissociate (i = 1), and NaCl dissociates into 2 ions.
Use the boiling point elevation formula: ΔTb = i * Kb * m, where ΔTb is the boiling point elevation, i is the van't Hoff factor, Kb is the ebullioscopic constant of the solvent, and m is the molality of the solution.
Compare the products of i * m for each compound, assuming equal molality, to determine which solution has the highest boiling point elevation. The compound with the highest product will have the greatest effect on the boiling point.
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