Basic Concepts| First Year Chemistry | Past MCQs | mosaicbro.com

Basic Concepts| First Year Chemistry | Past MCQs

7 of 41 questions (Page 4 of 6)

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22 The percentage of Nitrogen in NH₃ is:
Correct Answer: B
Explanation: % N = (14/17) × 100 = 82.35%.
23 NH₃ burns in O₂ according to the reaction: 4NH₃ + 3O₂ ⇌ 2N₂ + 6H₂O. Which statement is correct?
Correct Answer: A
Explanation: Stoichiometry: 4 moles NH₃ → 2 moles N₂ ⇒ 1 mole NH₃ → 0.5 mole N₂.
24 Molecular formula is equal to:
Correct Answer: A
Explanation: Molecular formula = (Empirical formula)ₙ.
25 The number of atoms present in 0.5 moles of Na is:
Correct Answer: D
Explanation: 0.5 moles × 6.02 × 10²³ atoms/mole = 3.01 × 10²³ atoms.
26 The atomicity of NH₃ is:
Correct Answer: D
Explanation: NH₃ has 4 atoms (1 N + 3 H).
27 Water absorber used in combustion analysis is:
Correct Answer: D
Explanation: Mg(ClO₄)₂ (anhydrone) is a potent desiccant.
28 The number of isotopes of oxygen is:
Correct Answer: D
Explanation: Oxygen has 3 stable isotopes: ¹⁶O, ¹⁷O, ¹⁸O.
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