Question

In a cold climate, water gets frozen causing damage to the car radiators. Ethylene glycol is used as an antifreeze. Calculate the amount of ethylene glycol to be added to 4 kg of water to prevent it from freezing at −6°C. (K_f for water = 1.85 K kg mol⁻¹)

Answer 1

Given: Final freezing point = −6°C = 267 K

Freezing point of pure water = 273 K

K_f for water = 1.85 K kg mol⁻¹

Mass of water (solvent) (w₁) = 4 kg

Molar mass of ethylene glycol = 62 g/mol

ΔT_f = 273 − 267 = 6 K

We know that,

`Delta T_f = K_f * w_2/(M * w_1)`

⇒ `w_2 = (Delta T_f * M * w_1)/K_f`

`w_2 = (6.62 xx 4)/1.85`

= `1488/1.85`

w₂ = 804.3 g

∴ The amount of ethylene glycol to be added is 804.3 g.