Answer: 100.95°C
Explanation:
1) The increase of the boiling point of a solution is a colligative property and its value is:
ΔTb = m × Kb × i
2) i is the Van't Hoof constant ans for non ionic solute is 1.
3) m is the molality
m = moles of solute / Kg of solvent
moles of solute = mass in grams / molar mass
molar mass of C₂H₅OH = 2 × 12.0 g/mol + 2 × 1.0 g/mol + 16.0 g/mol + 1.0 g/mol = 43.0 g/mol
moles of solute = 20.0 g / 43.0 g/mol = 0.465 mol
m = 0.465 mol / 0.250 kg = 1.86 m
3) Kb is the molal boiling constant of the solvent.
For water Kb = 0.512 °C / mol
4) ΔTb = 1.86m × 1 × 0.512 °C / mol = 0.95°C.
5) Boiling temperature
Tb = 100°C + 0.95°C = 100.95°C
