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).

Answer 1

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.