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Question
A gold sample contains 90% of gold and the rest copper. How many atoms of gold are present in one gram of this sample of gold?
Solution
1 g of gold sample contains = `90/100`
= 0.9g gold
Number of moles of gold = `"Mass of gold"/"Atomic mass of gold"`
= `0.9/197`
= 0.0046
1 mole of gold contains = 6.022 × 1023 atoms
0.0046 mole of gold = 6.022 × 1023 × 0.0046
= 2.77 × 1021 atoms
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