Question

An aqueous solution of a certain chemical is found to boil at 104.5 oC. At what temperature is this solution likely to freeze? The normal boiling point of water is

Answer 1

Answer:

16.4 °C

Explanation:

Boiling point elevation is the phenomenon in which the boiling point of a solvent will increase when another compound is added to it; meaning that athe resultant solution has a higher boiling point than its pure solvent.

Using the ebullioscopic constant,

ΔT = m * i * Kb

Where,

Δ T is the temperature difference between the boiling point of the solution, Temp.f and boiling point of the pure solvent, Temp.i

Kb is the ebulliscope factor of water = 0.510 °C.kg/mol

i is the van hoffs number = 1

m is the molality in mol/kg.

Calculating the molality of the solution,

Temp.i = 100°C

Temp.f = 104.5 °C

= 4.5/(1*0.510)

= 8.8235 mol/kg

Freezing point depression is defined as the decrease in the freezing point of a solvent on the addition of a solute.

Using the same equation, but kf = 1.86 °C.kg/mol

ΔT = m * i * Kf

Temp.i = freezing point of water = 0°C

Temp.f = (8.8235*1.86) - 0

= 16.412 °C

Freezing point of the solution = 16.4 °C