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)

$W=0.30g{V}_1=50ml$
$P_1=(P-a)=715-15=700mmofHg$
$T_1=300K$
Where a = aqueous tension
Now , $\frac{P_1{V}_1}{T_1}=\frac{P_2{V}_2}{T_2}$
$V_2=\frac{P_1{V}_1\times T_2}{T_1\times P_2}=\frac{700\times 50\times 273}{300\times 760}$
$V_2=41.9ml$
$\%ofnitrogen=\frac{28}{22400}\times \frac{41.9}{0.3}\times 100=17.46\%$