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WAEC Chemistry 2021 Objective — Question 44

Question 44 of 50 from the West African Examinations Council (WAEC) Chemistry 2021 Objective paper, with the correct answer and a full explanation.

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44. How many molecules of oxygen would occupy a volume of 2.24cm³ at s.t.p.? [Molar volume at s.t.p.=22,400cm³; Avogadro's number=6.02×10²³]

  • A. 3.01×10²⁰
  • B. 3.01×10²¹
  • C. 6.02×10¹⁹Correct
  • D. 6.02×10²⁷

Explanation

Moles = 2.24/22400 = 1×10⁻⁴ mol. Molecules = 1×10⁻⁴ × 6.02×10²³ = 6.02×10¹⁹.

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