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

Basic Concepts| First Year Chemistry | Past MCQs

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1 Which of the following compounds has the highest % age of oxygen by weight?
Correct Answer: D
Explanation: H₂O has 88.89% oxygen by weight, the highest among the options.
2 Formula mass of MgSO₄ is g/mole:
Correct Answer: B
Explanation: Mg (24) + S (32) + 4×O (16) = 120 g/mol.
3 Electrometer is also called:
Correct Answer: C
Explanation: An electrometer measures ion currents, hence called an ion collector.
4 In combustion analysis, H₂O vapors are absorbed by:
Correct Answer: B
Explanation: Mg(ClO₄)₂ is a strong desiccant used to absorb water.
5 Height of peak in mass spectrum shows:
Correct Answer: C
Explanation: Peak height correlates with the relative abundance of an isotope.
6 The volume occupied by 1.4 g of N₂ at S.T.P is:
Correct Answer: C
Explanation: 1.4 g N₂ = 0.05 moles; 0.05 × 22.4 dm³ = 1.12 dm³.
7 Molecular mass of CaCO₃ is:
Correct Answer: A
Explanation: Ca (40) + C (12) + 3×O (16) = 100 g/mol.
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