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 5.80 gallons, what is the boiling point of the solution? Make the following assunptions 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 (HOCH2CH20H), 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 Number

Explanation / Answer

Volume of solution = 5.80 gallons x 3.785L/gallon

= 21.953 L

Volume of ethylene glycol = 21.953/2 = 10.9765 L

Volume of water = 10.9765 L

Mass of ethylene glycol = volume x density

= 10.9765 L x 1000mL/L x 1.11 g/mL

= 12183.915 g

Mass of water = 10.9765 L x 1000mL/L x 0.998 g/mL

= 10954.547 g x 1kg/1000g

= 10.955 kg

Moles of ethylene glycol = mass/molecular weight

= 12183.915 g / 62.08g/mole

= 196.26 moles

Boiling point elevation

Boiling point of solution - boiling point of water = van't Hoff factor x Boiling point elevation constant x Molality

Ts - Tb = i x Kb x m

Ts - 100 °C = 1 x 0.512 °C/m x 196.26 moles / 10.955 kg

Ts - 100 = 9.172

Ts = 100 + 9.172

Ts = 109.172 °C

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