Question

Ethylene glycol is used as an antifreeze in car. if 400 g of ethylene glycol is added to 4.00 kg of water, what is the molaity? calcualte how much the freezing point of water will be lowered. The freezing point depression constant for water is Kf=-1.86

Answer 1

Data:

solute: ethylene glicol => not ionization

molar mass of ethylene glicol (from internet)  = 62.07 g/mol

solute  = 400 g

solvent = water = 4.00 kg

m =?

ΔTf = ?

Kf = 1.86 °C/mol

Formulas:

m: number of moles of solute / kg of solvent

ΔTf = Kf*m

number of moles of solute = mass in grams / molar mass

Solution

number of moles of solute = 400 g / 62.07 g/mol = 6.44 moles

m = 6.44 mol / 4 kg = 1.61 m <-------- molality (answer)

ΔTf = 1.86 °C / m * 1.61 m = 2.99 °C <---- lowering if freezing point (answer)