JEE Main · 2025 · 02 Apr 2025 · Shift 2 · Practical and Analytical Chemistry

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In Dumas' method for estimation of nitrogen, 0.5 gram 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 (Aqueous tension at

300 K = 15 mm Hg

) is

(A)1.257
(B)20.87
(C)18.67
(D)12.57✓ Correct

Answer: (D)

Solution

In Dumas' method the nitrogen is collected over water, so the pressure of dry nitrogen is

715 - 15 = 700 mm Hg

. The amount of nitrogen is

n = \frac{P V}{R T} = \frac{( 700/760 ) \times ( 60 \times 1 0 ^{- 3} )}{0.0821 \times 300} = 2.24 \times 1 0^{- 3} mol

, with mass

2.24 \times 1 0^{- 3} \times 28 = 0.0628 g

. The percentage of nitrogen is

\frac{0.0628}{0.5} \times 100 = 12.57%

JEE Main · 2025 · 02 Apr 2025 · Shift 2 · Single correct option

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