Question

In Dumas method for estimation of nitrogen 0.30 g of an organic compound gave 50 ml of nitrogen collected at 300 K and 715 mm of Hg pressure. The percentage composition of nitrogen in the compound is, if aqueous tension at 300 K is 15 mm of Hg.

• A. 37%
• B. 17%
• C. 57%
• D. 75%

Answer 1

Answer: (B)

$W = 0.30g \,\,\,\,\,\,\,V_1 = 50ml$
$P_1 =(P-a) = 715-15 = 700\, mm \,of\, Hg $
$T_1 = 300\,K$
Where a = aqueous tension
Now , $\frac {P_1V_1}{T_1} = \frac {P_2V_2}{T_2}$
$V_2 = \frac {P_1V_1 \times T_2}{T_1\times P_2}=\frac {700\times 50 \times 273}{300 \times 760}$
$V_2 = 41.9\,ml$
$\% \,of \, nitrogen = \frac {28}{22400} \times \frac {41.9}{0.3} \times 100 = 17.46 \%$