In Kjeldahl's method for estimation of nitrogen,$CuSO_4$ acts as :

During the estimation of $C$ and $H$,the $H_2O$ produced is absorbed in which of the following?

$0.5 \ g$ of an organic compound containing phosphorus was heated with conc. $HNO_3$ in a Carius tube. The phosphoric acid thus formed was precipitated with magnesia mixture $[MgNH_4PO_4]$,which on ignition gave a residue of $1.0 \ g$ of magnesium pyrophosphate $(Mg_2P_2O_7)$. The percentage of phosphorus in the organic compound is:

Explain the principle and estimation method for carbon and hydrogen in an organic compound.

Which method is used for the estimation of nitrogen in an organic compound?

Match column $-I$ and column $-II$ with the correct relation:

Column $-I$	Column $-II$
$(i)$ Dumas method	$(a)$ Absorption of $NH_3$ in $H_2SO_4$
$(ii)$ Kjeldahl's method	$(b)$ $BaCl_2$ by added $BaSO_4$
$(iii)$ Carius method	$(c)$ Mixture of Magnesia
$(iv)$ Estimation of phosphorus	$(d)$ $N_2$