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A sample of a gas has a mass of 7.5 g and occupies 5.6 L at STP. Which gas is it?

1. N₂O
2. NO
3. CO
4. CO₂

Correct answer: NO

Solution

5.6 L at STP = 0.25 mol; molar mass = 7.5/0.25 = 30 g/mol = NO. Stored CO (28 g/mol) is wrong.

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