What are the normal freezing points and boiling points of the following solutions?
(b) 13.5 g of urea in 65.6 mL of water. Calculate the freezing point and boiling point.
(b) 13.5 g of urea in 65.6 mL of water. Calculate the freezing point and boiling point.
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Calculate the molality of the urea solution:
(moles urea / kg of water)
13.5g x 1mole urea / 60.1g) / 0.0656kg water = 3.42molal.
FP = 0C - (3.42m x 1.86C/m) = -6.37C.
BP = 100C + (3.42m x 0.512C/m) = 101.75C
The molal freezing point constant for water is 1.86C/molal, meaning that a 1.86m solution (of a nonionizing solute) will lower the FP 1.86C.
Similarly the molal boiling point constant of water is 0.512C/m.
(moles urea / kg of water)
13.5g x 1mole urea / 60.1g) / 0.0656kg water = 3.42molal.
FP = 0C - (3.42m x 1.86C/m) = -6.37C.
BP = 100C + (3.42m x 0.512C/m) = 101.75C
The molal freezing point constant for water is 1.86C/molal, meaning that a 1.86m solution (of a nonionizing solute) will lower the FP 1.86C.
Similarly the molal boiling point constant of water is 0.512C/m.