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Chemistry NMDCAT MCQs Moles and Avogadro's Numbers
nmdcat.online July 2, 2026

A sample of a pure element weighing 0.64 g contains 6.022 × 10²¹ atoms. The atomic mass of the element is

A. 16 u
B. 32 u
C. 64 u
✓
D. 128 u

📝 Explanation

Number of moles = 6.022 × 10²¹ ÷ 6.022 × 10²³ = 0.01 mole. Atomic mass = 0.64 ÷ 0.01 = 64 g/mol (64 u).

📖 Additional Information

  • 16 u
  • 32 u
  • 64 u
  • 128 u

Number of moles = 6.022 × 10²¹ ÷ 6.022 × 10²³ = 0.01 mole. Atomic mass = 0.64 ÷ 0.01 = 64 g/mol (64 u).

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