Describe the principle and reactions involved in the estimation of oxygen in an organic compound.

In Dumas' method for estimation of nitrogen,$0.3 \ g$ of an organic compound gave $50 \ mL$ of nitrogen collected at $300 \ K$ temperature and $715 \ mm$ pressure. Calculate the percentage composition of nitrogen in the compound. (Aqueous tension at $300 \ K = 15 \ mm$)

Discuss the principle of estimation of halogens,sulphur and phosphorus present in an organic compound.

$0.3780 \, g$ of an organic chloro compound gave $0.5740 \, g$ of silver chloride in Carius estimation. Calculate the percentage of chlorine present in the compound. (in $\%$)

While estimating the nitrogen present in an organic compound by Kjeldahl's method,the ammonia evolved from $0.25 \ g$ of the compound neutralized $2.5 \ mL$ of $2 \ M \ H_2SO_4$. The percentage of nitrogen present in the organic compound is $......$

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	$(d)$ $N_2$