Question

The mass of a solid copper penny is 3.46 g. how many copper atoms are in the penny?

Answer 1

3.46 g Cu 1 mol Cu 6.02*10^23 atoms Cu =
63.55 g Cu 1 mol Cu

3.28*10^22 atoms Cu

Answer 2

n° atoms = 3.275x10²² atoms

Step-by-step explanation:

To do this, we need to use the molecular weight of the copper, which is 63.55 g/mol.

Now, to know the number of atoms of any compound, we use the avogadro number which is relationed to the number of moles of any compound so:

1 mol = 6.02x10²³ atoms

In order to know the atoms, we need to calculate the moles of copper with the following expression:

n = m/MW

Doing so, we have the moles, and then, use the avogadro number to calculate the atoms:

First the moles:

n = 3.46/63.55 = 0.0544 moles

Now, let's calculate the atoms:

n° atoms = n * Av. number

n° atoms = 0.0544 ¨* 6.02x10²³

n° atoms = 3.275x10²² atoms

This would be the atoms in the penny.