Ethylene glycol, the primary ingredient in antifreeze, has the chemical formula C2H6O2. The radiator fluid used in most cars is a half-and-half mixture of water and antifreeze. Part A What is the freezing point of radiator fluid that is 50% antifreeze by mass? Kf for water is 1.86 ∘C/m.

First, we have to calculate the molality (m) of the solution. If the solution is 50% C₂H₆O₂ by mass. It means that in 100 g of solution, the are 50 g of solute (C₂H₆O₂) and 50 g of solvent (water).

The molar mass of C₂H₆O₂ is 62.07 g/mol. The moles of solute are:

50 g × (1 mol / 62.07 g) = 0.81 mol

The mass of the solvent is 50 g = 0.050 kg.

The molality is:

m = 0.81 mol / 0.050 kg = 16 m

The freezing-point depression (ΔT) can be calculated using the following expression.

ΔT = Kf × m = (1.86 °C/m) × 16 m = 30 °C

where,

Kf: freezing-point constant

The normal freezing point for water is 0°C. The freezing point of the radiator fluid is:

0°C - 30°C = -30 °C