A 50/50 blend of engine coolant and water (by volume) is usually used in an auto

Question

A 50/50 blend of engine coolant and water (by volume) is usually used in an automobile's engine cooling system. If your car's cooling system holds 6.00 gallons, what is the boiling point of the solution?

Make the following assumptions in your calculation: at normal filling conditions, the densities of engine coolant and water are 1.11 g/mL and 0.998 g/mL respectively. Assume that the engine coolant is pure ethylene glycol (HOCH2CH2OH), which is non-ionizing and non-volatile, and that the pressure remains constant at 1.00 atm. Also, you'll need to look up the boiling-point elevation constant for water.

Explanation / Answer

Since there is 50/50 blend of engine coolant ,
Consider that you have 1 litre ,
gms of ethylene glycol , 500 mL * 1.11 g/mL = 555 gm
gms of water , 500mL * 0.998 g/mL = 499 gm
They asked you the boiling point of water, so let water be the solvent
moles of ethylene glycol = 555 gm / 62.07g/mol = 8.9415 moles
8.94 moles ------------------ 499 g of water ( consider molality, mol / kg of solvent)
? ----------------- 1000 g of water
cross multiply to get number of moles in 1kg of water
(1000g *8.94mol) / 499g = 17.9158 mol / Kg water = 17.9158 molal
Molal boiling point constant for water = 0.512 C / molal
B.p = 100 oC + ( 17.9158 molal * 0.512 C / molal ) = 109.17288 o C

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