Determine the required concentration (in percent by mass) for an aqueous ethylene glycol (C2H6O2) solution to have a boiling point of 107.1 oC.
We’re being asked to calculate the mass percent of ethylene glycol (C2H6O2) solution to have a boiling point of 107.1 oC.
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:
We go through the following steps to solve:
Step 1. Calculate the molality
Step 2. Calculate the mass of solute and solvent
Step 3. Calculate the mass percent