What are the new freezing and boiling points of water if 50 g of ethylene glycol(molecular mass = 62 g/mol) is added to 50 g of water?

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justaguide | College Teacher | (Level 2) Distinguished Educator

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When an impurity is dissolved in water the temperature at which water freezes drops and the temperature at which it boils rises. The change in the freezing point is given by dTf = Kf*cm and the change in the temperature at which it boils is given by dTb = Kb*cm, where Kf and Kb are constants for a liquid and cm is the the molality of the impurity.

Here, we have 50 g of ethylene glycol with a molecular mass of 62 g/mole. 50 g is 0.8065 mole. When this is dissolved in 50 g of water we get a molality of 0.8065/0.05 = 16.13

The constant Kf for water is 1.858 and Kb is 0.521.

The change in boiling point is 8.40 degrees Celsius or the new boiling temperature is 108.4 degrees Celsius.

The change in the freezing point is 29.96 degrees Celsius or the new freezing point is -29.96 degrees Celsius.

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