Question

If a penny is made of 3.11 grams of copper, how many atoms of copper are there in the penny? Show work.

a) Approximately 3.11 x 10^23 atoms
b) Approximately 6.02 x 10^23 atoms
c) Approximately 1.5 x 10^24 atoms
d) Approximately 9.81 x 10^22 atoms

Answer 1

The number of copper atoms in a penny weighing 3.11 grams is calculated using the atomic mass of copper and Avogadro's number, resulting in approximately 2.95 × 10²² atoms.

Step-by-step explanation:

To calculate the number of copper atoms in a penny weighing 3.11 grams, we can use Avogadro's number and the atomic mass of copper. First, we need to find out how many moles of copper we have:

Atomic mass of copper = 63.54 g/mol
Mass of the penny = 3.11 g

Number of moles = mass of copper ÷ atomic mass = 3.11 g ÷ 63.54 g/mol ≈ 0.04896 moles

Using Avogadro's number, which is approximately 6.02 × 1023 atoms per mole, we can calculate the number of copper atoms:

Number of atoms = number of moles × Avogadro's number
= 0.04896 moles × 6.02 × 1023 atoms/mol
≈ 2.95 × 1022 copper atoms

Therefore, the approximate number of copper atoms in a penny weighing 3.11 grams is 2.95 × 1022 atoms, which corresponds to option (a).