An aqueous solution of urea freezes at −0.186oC. Kf for water = 1.86Kkgmol−1, Kb for water = 0.512Kkgmol−1. The boiling point of urea solution will be :
A
373.065 K
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B
373.186 K
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C
373.512 K
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D
373.0512 K
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Solution
The correct option is B373.0512 K Given that,
Kf=1.86Kkg/mol;Kb=0.512Kkg/mol;Tf,solution=−0.186oC and Tf,water=0oC
ΔTf=0.186K
Since,
ΔTfKf=ΔTbKb=m
ΔTb=0.1861.86×0.512=0.0512K
As, Tb,water=373K, and
ΔTb=0.0512K
Since there is an elevation in boiling point upon addition of solute