posted by Danya .
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!
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.
2.4x10^24 copper atoms
.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