When sodium fusion extract of an organic compound is boiled with iron (II)sulphate solution followed by addition of concentrated $\mathrm{H}_2 \mathrm{SO}_4$, gives prussian blue colour. This confirms the presence of the element

Which of the following compounds will be suitable for estimation of nitrogen by Kjeldahl's method?

During the course of estimating nitrogen using Kjeldahl's method, the organic compound is heated with

Which one of the following methods is suitable to separate a mixture of $n$-pentane and toluene?