JEE Main · 2026 · 24 Jan 2026 · Shift 1 · Practical and Analytical Chemistry

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In Dumas method for estimation of nitrogen, 0.50 g of an organic compound gave 70 mL of nitrogen collected at 300 K and 715 mm pressure. The percentage of nitrogen in the organic compound is ______ %
(Aqueous tension at 300 K is 15 mm ).

Answer: 15

Solution

Correcting for aqueous tension, the pressure of nitrogen is

715 - 15 = 700 mm

. The moles of

N_{2}

are

n = \frac{P V}{R T} = \frac{( 700/760 ) ( 0.070 )}{0.0821 \times 300} = 2.62 \times 1 0^{- 3}

, so the mass of nitrogen is

2.62 \times 1 0^{- 3} \times 28 = 0.0733 g

. The percentage of nitrogen is

\frac{0.0733}{0.50} \times 100 = 14.7%

, which rounds to

15%

JEE Main · 2026 · 24 Jan 2026 · Shift 1 · Integer answer

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