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O Levels Chemistry (5070)•5070/12/M/J/19
Question 11 from 5070/12/M/J/19

Explanation

Equal moles via atomic masses for same atom count

Steps:

  • Atomic mass of sulfur is 32 g/mol, so moles in 16 g = 16 / 32 = 0.5 mol.
  • Same number of atoms requires 0.5 mol of carbon.
  • Atomic mass of carbon is 12 g/mol, so mass = 0.5 mol × 12 g/mol = 6 g.
  • Thus, 6 g of carbon has the same atoms as 16 g of sulfur.

Why B is correct:

  • 6 g of carbon equals 0.5 mol (6/12), matching 0.5 mol of sulfur (16/32), so equal atoms per Avogadro's number.

Why the others are wrong:

  • A: 0.5 g carbon is ~0.042 mol (0.5/12), fewer atoms than 0.5 mol sulfur.
  • C: 8 g carbon is ~0.667 mol (8/12), more atoms than 0.5 mol sulfur.
  • D: 12 g carbon is 1 mol (12/12), twice the atoms of 0.5 mol sulfur.

Final answer: B

Topic: The mole and the Avogadro constant

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