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

Basic Concepts| First Year Chemistry | Past MCQs

7 of 41 questions (Page 5 of 6)

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29 A limiting reactant is that one which:
Correct Answer: A
Explanation: Limiting reactant determines the minimal product yield.
30 Atoms of which one of the following element have independent existence:
Correct Answer: B
Explanation: Noble gases (e.g., Kr) exist as monoatomic species.
31 Dempster’s mass spectrometer was designed for the identification of isotopes of the elements which were available in:
Correct Answer: C
Explanation: Early mass spectrometers analyzed solids (vaporized into gases).
32 One of the substances is used to absorb CO₂ gas in combustion analysis which is that substance:
Correct Answer: A
Explanation: KOH absorbs CO₂ via the reaction: 2KOH + CO₂ → K₂CO₃ + H₂O.
33 Number of molecules in one dm³ of H₂O is close to:
Correct Answer: C
Explanation: 1 dm³ H₂O = 1000 g ≈ 55.5 moles → 55.5 × 6.022 × 10²³ molecules.
34 The volume occupied by 32 g of O₂ at S.T.P is:
Correct Answer: A
Explanation: 32 g O₂ = 1 mole → occupies 22.414 dm³ at STP.
35 Silver has isotopes:
Correct Answer: B
Explanation: Silver has 2 stable isotopes (¹⁰⁷Ag, ¹⁰⁹Ag), but 16 total known isotopes.
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