Solutions

Solutions

Question

Kf for water is 1.86K kg mol–1.If your automobile radiator holds 1.0 kg of water, how many grams of ethylene glycol (C2H6O2) must you add to get the freezing point of the solution lowered to –2.8°C?

  • 72 g

  • 93 g

  • 39 g

  • 27 g

Answer

B.

93 g

Coolant is glycol (C2H6O2) and is non-electrolyte.
ΔTf =2.8°
increment straight T subscript straight f space equals space fraction numerator 1000 space straight x space straight K subscript straight f space straight x space straight w subscript 1 over denominator straight m subscript 1 straight w subscript 2 end fraction space rightwards double arrow
2.8 space equals space fraction numerator 1000 space straight x space 1.86 space straight x space straight w subscript 1 over denominator 62 space straight x space 1000 end fraction
therefore straight w subscript 1 space equals space 93.33 space straight g

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