Explain the estimation of nitrogen of an organic compound by
a) Dumas method

Explanation

Estimation of nitrogen by Duma's method :
In this method a known weight of organic compound is heated strongly with coarse cupric oxide. Then carbon and hydrogen get oxidised to `CO_(2)` and `H_(2)O` vapour respectively. Nitrogen is converted to `N_(2)` gas some nitrogen cnverted into its oxides, gets reduced by copper gauze to nitrogen. The liberated gases are passed over a solution of KOH. Then `O_(2)` gets absorbed. Nitroegen is collected over KOH solution and its volume is found out.
Calculation :
Suppose 'a' g of organic compound gives V ml of `N_(2)` gas at room temp. TK.
Vol. of `N_(2)` gas at STP is calculated as follows.
`{:("Expt. conditions","STP condition"),(P_(1)=(P-p)" mm where",P_(2)=760 mm),("p = aqueous tension ",),(T_(1)=TK,T_(2)=273K),(V_(1)=V,V_(2)=?):}`
`(P_(1)V_(1))/(T_(1))=(P_(2)V_(2))/(T_(2))`
`rArr V_(2)=(P_(1)V_(1)T_(2))/(P_(2)T_(1))=((P-p)xxVxx273)/(760 xxT)=" x ml"`
`"22,400 ml. of "N_(2)" at STP weighs 28 g"`
`therefore" x ml. of "N_(2)" at STP weighs .............."?`
`=(x xx28)/(22,400)g`
'a' g of organic compound contains `(28 xx x)/(22400) g " of "N_(2)`
`therefore" 100 g of organic compound contains"`?
`=(100)/(a)xx(28xx x)/(22400)" g of "N_(2)`