Question

In Duma's method of estimation of nitrogen, 0.1840 g of an organic compound gave 30 mL of nitrogen collected at 287 K and 758 mm of Hg pressure. The percentage composition of nitrogen in the compound is ___. (Round to the nearest integer). [Given: Aqueous tension at 287 K = 14 mm of Hg]

Answer 1

Pressure of N = 758 - aqueous tension (mm of Hg)
From PV = nRT,
$\text{Moles of}{N}_2=\frac{758-14}{760}\times \frac{30\times {10}^{-3}}{0.0821\times 287}$

$=1.246\times {10}^{-3}\text{mol}$

$\text{Mass of}N=1.246\times {10}^{-3}\times 28$

$\text{Mass \% of 'N'}=\frac{massofN}{totalmass}\times 100$

$=\frac{1.246\times 28\times {10}^{-3}}{0.184}\times 100$

$=\frac{1.246\times 28}{0.184}=18.9\%$

Nearest integer = 19%