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Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
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Ch.12 - Solutions
Ch.13 - Chemical Kinetics
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Ch.23 - Transition Metals and Coordination Compounds

Solution: The boiling point of ethanol (C2H5OH) is 78.5°C. What is the boiling point of a solution of 6.4 g of vanillin (ℳ = 152.14 g/mol) in 50.0 g of ethanol (Kb of ethanol = 1.22°C/m)?

Solution: The boiling point of ethanol (C2H5OH) is 78.5°C. What is the boiling point of a solution of 6.4 g of vanillin (ℳ = 152.14 g/mol) in 50.0 g of ethanol (Kb of ethanol = 1.22°C/m)?

Problem

The boiling point of ethanol (C2H5OH) is 78.5°C. What is the boiling point of a solution of 6.4 g of vanillin (ℳ = 152.14 g/mol) in 50.0 g of ethanol (Kb of ethanol = 1.22°C/m)?

Solution

We’re being asked to determine the boiling point of a solution. The solution is composed of 6.4 g vanillin in 50.0 g ethanol


Recall that the boiling point of a solution is higher than that of the pure solvent and the change in boiling point (ΔT­b) is given by:



The change in boiling point is also related to the molality of the solution:



where: 

i = van’t Hoff factor

m = molality of the solution (in m or mol/kg)

Kb = boiling point elevation constant (in ˚C/m)


Recall that the molality of a solution is given by:



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