JEE Main 2025 Apr 3 Shift 1, Chemistry Q21: Principles Of Qualitative Analysis

JEE Main2025Apr 3, Shift 1Chemistry

During estimation of nitrogen by Dumas' method of compound X (0.42 g) :

__________ mL of $N_{2}$ gas will be liberated at STP. (nearest integer)

(Given molar mass in g mol $^{- 1}$ : C : 12, H : 1, N : 14)

Your answer

Solution

The compound shown (piperazine, $C_{4} H_{10} N_{2}$ ) has molar mass

$M = 4 (12) + 10 (1) + 2 (14) = 48 + 10 + 28 = 86 g mol^{- 1}$ .

Moles of X: $n_{X} = \frac{0.42}{86} mol$ .

Each molecule contains 2 N atoms, which combine to give 1 molecule of $N_{2}$ . By POAC on nitrogen, $n_{N_{2}} = n_{X} = \frac{0.42}{86} mol$ .

Volume at STP: $V = n_{N_{2}} \times 22.4 L = \frac{0.42}{86} \times 22.4 \approx 0.1094 L \approx 109.4 mL$ .

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