During estimation of nitrogen by Dumas' method of compound X (0.42 g): _____ mL of $\mathrm{N}_{2}$ gas will be liberated at STP. (nearest integer) (Given molar mass in $\mathrm{g} \mathrm{mol}^{-1}$: C: 12, H: 1, N : 14)

JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Practical and Analytical Chemistry

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)

Answer: 111

Solution

Compound X is piperazine,

C_{4} H_{10} N_{2}

, of molar mass

86 g mol^{- 1}

. In the Dumas method all nitrogen is set free as

N_{2}

; the two nitrogen atoms of each molecule give one

N_{2}

, so the moles of

N_{2}

equal the moles of compound,

\frac{0.42}{86} = 4.88 \times 1 0^{- 3}

. At STP one mole of gas occupies

22.7

L, so the volume is

4.88 \times 1 0^{- 3} \times 22700 \approx 111 mL

. The volume of nitrogen liberated is

111

mL.

JEE Main · 2025 · 03 Apr 2025 · Shift 1 · Integer answer

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