Question

Ethylene glycol is used as an antifreeze agent. 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 H₂O = 1 .85 K mole^-1 kg)

Answer 1

Depression in freezing point, `ΔT_f = (1000 xx K_f xx w)/(W xxM )`

Given ,                                         W = 4 kg = 4000 g 

                                                     K_f = 1.85

                                                   ΔT_f = 0 -(-6°) = 6° C

Mol. mas (M) of ethylene glycol CH₂ OH - CH₂ OH = 62 

∴ Amount of ethylene glycol required, 

                     `w = (MxxW xx Delta T_f)/(1000 xx K_f)`

                       `=(62xx4000xx6)/(1000xx1.85) = 804.32`g.