Question

Calculate the boiling point of a solution of 500.0 g of ethylene glycol (C2H6O2) dissolved in 500.0 g of water. Kf = 1.86°C/m and Kb = 0.512°C/m. Use 100°C as the boiling point of water.

Answer 1

Answer:

The boiling point of a solution of 500.0 g of ethylene glycol dissolved in 500.0 g of water is 108.258°C.

Explanation:

Elevation in boiling point : $\Delta T_b$

$\Delta T_b=T_b-T$

$\Delta T_b=K_b\times m$

$T_b$ = Boiling point of the solution

T = Boiling point of pure solvent

$K_b$= Molal elevation constant of solvent

m = molality of the solution

Molality of the  ethylene glycol solution:

$molality=\frac{\text{Moles of solute}}{\text{Mass of solvent in kg}}$

Moles of ethylene glycol = $\frac{500.0 g}{62 g/mol}=8.0645 mol$

Mass of solvent that uis water = 500.0 g = 0.5000 kg

$m=\frac{8.0645 mol}{0.5000 kg}=16.1290 m$

Molal elevation constant of water =$K_b=0.512^oC/m$

$\Delta T_b=0.512^oC/m\times 16.1290 m=8.258^oC$

Boiling point of the solution =$T_b$

Boiling point of pure water = T = 100°C

$T_b=T+\Delta T_b=100^oC+8.258^oC=108.258^oC$

The boiling point of a solution of 500.0 g of ethylene glycol dissolved in 500.0 g of water is 108.258°C.