Answer:
To produce a solution that frees at -50°C we need 1668.5 g of ethylene glycol
Step-by-step explanation:
Formula for freezing point depression is:
Freezing T° of pure solvent - Freezing T° of solution = Kf . m . i
Our solute is the ethylene glycol, then water is our solvent.
As ethylene glycol is a non ionic compound, i = 1 (Van't Hoff factor, numbers of ions dissolved)
Kf = Cryoscopic constant. For water is 1.86 °C/m
We replace data:
0°C - (-50°C) = 1.86 °C/m . m . 1
To determine grams of ethylene glycol needed, we need to find m (molality)
50°C / 1.86 m/°C = m → 26.8 mol/kg
As this moles of solute are contained in 1kg, definetely we need 26.8 moles of ethylene glycol.
To find the answer, we convert moles to mass:
26.8 mol . 62.07g / mol = 1668.5 g