Nitrous oxide is 36% oxygen by mass.

• A. True
• B. False
• C. 28%
• D. 44%

Answer: (A)

Mass percent by mass comes from dividing the mass of the part by the total molar mass of the compound. For nitrous oxide, the formula is N2O, so there are two nitrogens and one oxygen. Using approximate atomic masses (N ≈ 14.01, O ≈ 16.00), the molar mass is 2×14.01 + 16.00 ≈ 44.02 g/mol. The oxygen portion is 16.00 g, so the oxygen mass percent is (16.00 / 44.02) × 100 ≈ 36.4%. That matches the statement of about 36% oxygen by mass, so it’s correct. The other options would require oxygen contributing about 28% or 44% of the total mass, which doesn’t fit the actual masses and composition of N2O.