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

Basic Concepts| First Year Chemistry | Past MCQs

7 of 41 questions (Page 3 of 6)

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15 An ordinary microscope can measure size of object up to:
Correct Answer: D
Explanation: Limited by the wavelength of visible light (~500 nm).
16 How many times a hemoglobin molecule is heavier than hydrogen atom?
Correct Answer: C
Explanation: Hemoglobin (64,500 amu) is ~68,000× heavier than H (1 amu).
17 Isotopes are sister atoms of same element with similar chemical properties but different:
Correct Answer: C
Explanation: Isotopes differ in neutron number (atomic weight), not proton number (atomic number).
18 The volume occupied by 28 g of N₂ at STP is:
Correct Answer: A
Explanation: 28 g N₂ = 1 mole → occupies 22.414 dm³ at STP.
19 One mole of SO₂ contains:
Correct Answer: C
Explanation: 1 mole SO₂ contains 1 mole (6.02 × 10²³ atoms) of sulfur.
20 The pressure of vapors maintained in ionization chamber of mass spectrometer during isotopic analysis is:
Correct Answer: C
Explanation: Ultra-low pressure (~10⁻⁷ torr) avoids collisions between ions.
21 18.02 g of H₂O sample has:
Correct Answer: D
Explanation: 18.02 g H₂O = 1 mole = 6.022 × 10²³ molecules.
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