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Chemistry

A modern penny weighs 2.5 g but contains only .063 g of copper. How many copper atoms are present in a modern penny? Thanks in advance for any help you can give!

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  1. How many mols Cu are in the penny?
    That's mols Cu = grams Cu/atomic mass Cu.
    Then mols Cu x 6.02E23 = atoms Cu.

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  2. 2.4x10^24 copper atoms

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  3. 2.41x10^24

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  4. .065 g/1 x 1 mol/106.546 g x(6.022 x 10^24
    gives you a total of 3.67 x 10^21 atoms of Cu in .065 g of Cu

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