Which of the following `0.1 M` aqueous solutions will have the lowest freezing point?

Options

A. Sodium chloride
B. Potassium sulphate
C. Glucose
D. Urea

Answer

2

Explanation

Lowest freezing point implies highest `DeltaT_(f)` which in turn demands maximum value of van't hoff factor:
`DeltaT_(f)=I K_(f)m`
Here all the solutions have same concentraction `(0.1 M~~0.1 m)`.
`K_(2)SO_(4) overset(H_(2)O)(rarr) 2K^(+)+SO_(4)^(2-)`
`i=3`
`NaCl overset(H_(2)O)(rarr) Na^(+)+Cl^(-)`
`i=2`
Both glucose and urea neither dissciate nor associate, thus, both have `i=1`.