In Dumas' method for estimation of nitrogen 0.4 g of an organic compound gave 60 mL of nitrogen collected at 300 K temperature and 715 mm Hg pressure. The percentage composition of nitrogen in the compound is (Given : Aqueous tension at 300 K = 15 mm Hg)
- 15.71\%
- 17.46\%
- 7.85\%
- 20.95\%
Answer
(1) 15.71\%
Solution
Pressure of dry nitrogen = observed pressure − aqueous tension
pN2 = 715 - 15 = 700 mm Hg
Volume of dry N2 at STP (273 K, 760 mm Hg):
V0 = p1V1T1 T0p0
= 700 60300 273760
= 50.29 mL
22400 mL of N2 at STP weighs 28 g,
mass of N2 = 28 50.2922400 = 0.0629 g
\% N = 0.06290.4 100
= 15.71\%
Answer: (1)