Question

In Dumas method, 0.5 g of an organic compound containing nitrogen gave 112 ml of nitrogen at S.T.P. The percentage of nitrogen in the compound is:

• A. $28$
• B. $38$
• C. $18$
• D. $48$

Answer 1

The correct option is A $28$

Mass of the organic compound $=0.5$ $gm$

Volume of $N_2=112$ $mL$

Moles of $N_2=\frac{112}{22.4\times 1000}=5\times {10}^{-3}$ $moles$

Mass of $N_2=28\times 5\times {10}^{-3}=140\times {10}^{-3}$ $gm$

$\%N_2=\frac{Massof{N}_{2}atSTP}{Massofsubstancetaken}\times 100=\frac{140\times {10}^{-3}}{0.5}\times 100=28\%$