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Question
Calculate the number of atoms in 39.4 g gold. Molar mass of gold is 197g mole–1.
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Solution
We know that,
Molar mass = Mass of Avogadro's number of atoms (Molecules).
= 6.023 × 1023 atoms.
Given, molar mass of gold = 197 g/mol
Now,
∴ 197 g of gold contains = 6.023 × 1023 atoms
∴ 1 g of gold contain = `(6.023 xx 10^23)/197` atoms
∴ 39.4 g of gold contains = `(6.023 xx 10^23 xx 39.4)/197`
⇒ 1.20 × 1023 atoms.
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