Answer:
x = 4.45 * 10 ^22 Note. Technically, this should be rounded to 4.5 * 10^22. There are only 2 sig digits.
Explanation:
You have to assume that the coin is pure copper, which I doubt. What a coin is actually made of depends on when it was minted. But for the sake of this question, we'll assume coins are pure copper.
Copper has an atomic mass of 63.546 grams / mol
So 4.7 g of copper = 4.7 / 63.545 mol
We have 0.07396 mol of copper
1 mol of anything = 6.02 * 10^23 atoms (in this case).
0.07396 mol = x
Cross Multiply
1 * x = 0.07396 * 6.02 * 10^23
x = 4.45 * 10 ^22 atoms of copper
