Hey!
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Mass of the alloy:
m = 8.48 g/cm^3 * 125.5 cm^3 = 954 grams
954 * 0.37 = 352.98 grams
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Mass of the copper:
954 - 352.98 = 601.02 grams
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Copper Molar Mass: 63.55 g/mol
Zinc Molar Mass: 65.38 g/mol
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Moles in copper: 352.98 / 65.38 = 5.40 moles!
Moles in zinc: 601.02 / 63.55 = 9.46 moles!
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Atoms in copper = 10^24 * 3.25 atoms
Atoms in zinc = 10^24 * 5.70
I used the Avogadro's Number.
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Hope This Helped! Good Luck!