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WAEC Chemistry 2014 Objective — Question 17

Question 17 of 50 from the West African Examinations Council (WAEC) Chemistry 2014 Objective paper, with the correct answer and a full explanation.

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The mass of 800cm³ of a gas Q at s.t.p. is 1.0g. What is the molar mass of Q? [Avogadro's constant=22.4 gmol⁻¹]

  • A. 18 mol⁻¹
  • B. 28.0 gmol⁻¹
  • C. 28.0 gmol⁻¹Correct
  • D. 36.0 gmol⁻¹

Explanation

1g occupies 800cm³, so 1 mole (22400cm³) weighs (1/800)×22400 = 28g. Hence the molar mass of the gas is 28g/mol.

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