Kjeldahl's method cannot be used to estimate nitrogen for which of the following compounds?

A flask contains a mixture of isohexane and 3-methylpentane. One of the liquids boils at 63^oC while the other boils at 60^oC What is the best way to separate the two liquids and which one will be distilled out first ?

A chromatography column, packed with silica gel as stationary phase, was used to separate a mixture of compounds consisting of (A) benzanilide (B) aniline and (C) acetophenone. When the column is eluted with a mixture of solvents, hexane : ethylacelate (20:80), the sequence of obtained compounds is :

The increasing order to P_kb for the following compounds will be :