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)?
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:
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: