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Question
Assume that each atom in a copper wire contributes one free electron. Estimate the number of free electrons in a copper wire of mass 6.4 g (take the atomic weight of copper to be 64 g mol−1).
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Solution
Atomic weight of copper = 64 grams
No. of moles in 64 g of copper = 1
∴ No. of moles in 6.4 g of copper = 0.1
No. of atoms in 1 mole of copper = 6 × 10−23 = Avogadro's Number
No. of atoms in 0.1 mole = (6 × 10−23 × 0.1) = 6 × 1022
1 atom contributes 1 free electron.
∴ 6 × 1022 atoms contribute 6 × 1022 free electrons.
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