JEE Main 2025 Apr 2 Shift 2, Chemistry Q20: Mole Concept And Equivalent Concept

JEE Main2025Apr 2, Shift 2Chemistry

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

Solution

Correcting the pressure for aqueous tension: $P_{N_{2}} = 715 - 15 = 700 mm Hg$ .

Applying the ideal gas equation with $V = 60 mL = 60 \times 1 0^{- 3} L$ , $T = 300$ K:

$n_{N_{2}} = \frac{P V}{R T} = \frac{( 700/760 ) \times 60 \times 1 0 ^{- 3}}{0.0821 \times 300} \approx 2.24 \times 1 0^{- 3} mol$ .

Mass of nitrogen $= 2.24 \times 1 0^{- 3} \times 28 \approx 0.0627 g$ .

$% N = \frac{0.0627}{0.5} \times 100 \approx 12.57 %$ .

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JEE Main 2025 Apr 2 Shift 2, Chemistry Q20: Mole Concept And Equivalent Concept

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