A gas has a density of 1.25 g dm⁻³ at STP. Which of these gases could it be?
Correct answer B. N₂
Explanation
Molar mass = density × molar volume = 1.25 g dm⁻³ × 22.4 dm³ mol⁻¹ = 28 g mol⁻¹, which matches N₂. O₂ is 32, CO₂ is 44 and NH₃ is 17 g mol⁻¹.
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