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Question
Calculate the boiling point of urea solution when 8.0g of urea is dissolved in 250g of water. Boiling point of pure water is 373K.
(kb of water = 0.52 K kg mol-1, molecular mass of urea = 60 g mol-1)
Solution
To calculate the boiling point of a urea solution, the boiling point elevation formula:
ΔTb = i × kb × m
where,
ΔTb = 0.277 K (boiling point elevation)
i = Van't Hoff factor
Kb = 0.52 K·kg/mol
m = molality of the solution.
As we know,
`"T"_"solution" = "T"_"pure solvent" + Δ"T"_"b"`
`"T"_"solution"` = 373 K + 0.277 K
`"T"_"solution"` = 373.277 K
∴ boiling point of the urea solution is 373.277 K
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