In Dumas' method 292 mg of an organic compound released 50 mL of nitrogen gas (N2) at 300 K temperature and 715 mm Hg pressure. The percentage composition of 'N' in the organic compound is % (Nearest integer) (Aqueous tension at 300 K = 15 mm Hg)
Answer
18
Solution
Pressure of dry N2 = 715 − 15 = 700 mm Hg
Moles of N2: n = pVRT
= (700/760) atm 0.050 L0.0821 L atm K-1 mol-1 300 K
= 1.87 10-3 mol
Mass of nitrogen = 1.87 10-3 28 = 0.0524 g = 52.4 mg
\% N = 52.4292 100 = 17.9\% 18\%
Answer: 18