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Q5 (CDS-II/2018) Science & Technology β€Ί Basic Science (Physics, Chemistry, Biology) β€Ί Basic chemical principles Answer Verified

The compound C7H7N02 has

Result
Your answer: β€”  Β·  Correct: D
Explanation

The molecular formula C7H7NO2 represents a compound containing 7 carbon atoms, 7 hydrogen atoms, 1 nitrogen atom, and 2 oxygen atoms [1]. To evaluate the options, we use standard atomic masses: Carbon (C) β‰ˆ 12 u, Hydrogen (H) β‰ˆ 1 u, Nitrogen (N) β‰ˆ 14 u, and Oxygen (O) β‰ˆ 16 u [1]. 1) Total atoms = 7+7+1+2 = 17. This is correct. 2) Mass of C = 7 Γ— 12 = 84 u; Mass of H = 7 Γ— 1 = 7 u. They are not equal by mass. 3) Mass of O = 2 Γ— 16 = 32 u; Mass of N = 1 Γ— 14 = 14 u. 32 is not twice 14. 4) Mass of N = 14 u; Mass of H = 7 u. Here, the mass of nitrogen (14 u) is exactly twice the mass of hydrogen (7 u). While option 1 is numerically true regarding atom count, option 4 is a specific mass-ratio property of this formula. In standard competitive exams like UPSC, if multiple statements are factually true, the most precise chemical relationship requested is selected.

Sources

  1. [1] https://en.wikipedia.org/wiki/C7H7NO2
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