Category: Chemical Engineering Math
"Published in Newark, California, USA"
What is the freezing point of a 30% urea, (NH2)2CO solution in water?
Solution:
Basis: 100 grams of 30% (NH2)2CO
The
freezing point constant is defined as the number of degrees the
freezing point will be lowered per mole of solute per 1000 g or 1 kg of
solvent present. This can be written as
where m is the molality of a solution.
The number of moles of (NH2)2CO is
The weight of water is
Hence, the molality of 30% (NH2)2CO solution in water is
From the Table of Freezing and Boiling Information of Solvents, the freezing point constant of water is .
The
freezing point depression is defined as the product of the freezing
point constant of a solvent and the molality of a solution.
Hence, the freezing point depression of a solution is
Therefore, the freezing point of 30% (NH2)2CO solution is