Answer:
The lowest possible melting point for engine coolant is -12.8°C
Explanation:
This is about colligative property about freezing point depression.
We think the data 30% as a %m/m. It means that 30 g of ethylene glycol are contained in 100 g of solution. Therefore, we have 70 g of solvent.
Formula for freezing point depression is:
ΔT = Kf . m . i
Where ΔT = Freezing T° of pure solvent - Freezing T° of solution.
Freezing T° of solvent = 0° (We talk about water)
Let's determine m (molality, moles of solute in 1kg of solvent)
70 g = 0.070 kg
30 g . 1 mol / 62.07 g = 0.483 moles
0.483 mol / 0.070 kg = 6.90 m
We replace data in formula:
0° - Freezing T° of solution = 1.86 °C/m . 6.90m . 1
As ethylene glycol is a nonelectrolyte, i = 1
Freezing T° of solution = - 12.8°C
