We’re being asked to **calculate the mass percent of ethylene glycol (C _{2}H_{6}O_{2}) solution to have a boiling point of 107.1 ^{o}C.**

Recall that the boiling point of a solution is *higher* than that of the pure solvent and the ** change in boiling point (ΔT_{b})** is given by:

$\overline{){\mathbf{\u2206}}{{\mathbf{T}}}_{{\mathbf{b}}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}{{\mathbf{T}}}_{\mathbf{b}\mathbf{,}\mathbf{}\mathbf{solution}}{\mathbf{}}{\mathbf{-}}{\mathbf{}}{{\mathbf{T}}}_{\mathbf{b}\mathbf{,}\mathbf{}\mathbf{pure}\mathbf{}\mathbf{solvent}}{\mathbf{}}}$

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

$\overline{){\mathbf{\u2206}}{{\mathbf{T}}}_{{\mathbf{b}}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}{{\mathbf{iK}}}_{{\mathbf{b}}}{\mathbf{m}}}$

where:

**i** = van’t Hoff factor

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

**K _{b}** = boiling point elevation constant (in ˚C/m)

Recall that the ** molality of a solution** is given by:

$\overline{){\mathbf{Molality}}{\mathbf{}}{\mathbf{\left(}}{\mathbf{m}}{\mathbf{\right)}}{\mathbf{}}{\mathbf{=}}{\mathbf{}}\frac{\mathbf{moles}\mathbf{}\mathbf{of}\mathbf{}\mathbf{solute}}{\mathbf{Kilograms}\mathbf{}\mathbf{of}\mathbf{}\mathbf{solvent}}}$

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

Determine the required concentration (in percent by mass) for an aqueous ethylene glycol (C_{2}H_{6}O_{2}) solution to have a boiling point of 107.1 ^{o}C.

Frequently Asked Questions

What scientific concept do you need to know in order to solve this problem?

Our tutors have indicated that to solve this problem you will need to apply the Boiling Point Elevation concept. If you need more Boiling Point Elevation practice, you can also practice Boiling Point Elevation practice problems.