Q39Long answer
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?
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One gram of gold sample will contain = 0.9 g of gold Mass of gold Number of moles of gold = Atomic mass of gold 0.9 = = 0.0046 One mole of gold contains NA atoms = 6.022 ×1023 ∴ 0.0046 mole of gold will contain = 0.0046 × 6.022 ×1023 = 2.77×1021