Question

Which one of the following aqueous solutions will exhibit highest boiling point?

• A. $ 0.01\,M\,N{{a}_{2}}S{{O}_{4}} $
• B. $ 0.01\,M\,KN{{O}_{3}} $
• C. $ 0.015\,M\,\text{urea} $
• D. $ 0.015\,M\,\text{glucose} $

Answer 1

Answer: (A)

Boiling point $ ={{T}_{0}}(Solvent)+{{T}_{b}} $ (Elevation in b. p.)
$ \Delta {{T}_{b}}=mi{{k}_{b}} $
where, m is the molality ie, the van't Hoff factor (i)
$ =[1+(y-1)x] $ $ {{k}_{b}}= $
molal elevation constant.
Thus, $ \ \Delta {{T}_{b}}\propto im $
Assume 100% ionization [a]
$ mi(N{{a}_{2}}S{{O}_{4}})=0.01\times 3=0.03 $ [b]
$ mi(KN{{O}_{3}})=0.01\times 2=0.02 $ [c] $ mi(glucose)=0.015 $