The depression in freezing point of `0.01 m` aqueous `CH_(3)CooH` solution is `0.02046^(@)`, `1 m` urea solution freezes at `-1.86^(@)C`. Assuming molality equal to molarity, `pH` of `CH_(3)COOH` solution is

Options

A. 2
B. 3
C. `3.2`
D. `4.2`

Explanation

For urea
`DeltaT_(t)=K_(t)xxm` or `K_(t)=(DeltaT_(t))/(m)=(1.86)/(1)=1.86`
Now for `CH_(3)COOH`
`DeltaT_(t)=i K_(t)m`
so `i=(0.02046)/(1.86xx0.01)=1.1`
Now `i=1+alpha`
so `alpha=1.1-1=0.1`
Now `{:(CH_(3)COOH,hArr,CH_(3)COO^(-),+,H^(+)),(" "C,,0,,0),(C-Calpha,,Calpha,,Calpha):}`
`[H^(+)]=Calpha=0.1xx0.1=0.001`
so `pH=3`.