Questions: How many atoms of copper are in a pure copper penny that weighs 2.15 g ? (1 amu=1.6605 x 10^-24 g)

Solution Steps

The molar mass of copper (Cu) is approximately \(63.55 \, \text{g/mol}\).

Use the formula: \[ \text{Number of moles} = \frac{\text{mass of copper}}{\text{molar mass of copper}} \] Substitute the given values: \[ \text{Number of moles} = \frac{2.15 \, \text{g}}{63.55 \, \text{g/mol}} \]

Use Avogadro's number, \(6.022 \times 10^{23} \, \text{atoms/mol}\), to find the number of atoms: \[ \text{Number of atoms} = \text{Number of moles} \times 6.022 \times 10^{23} \, \text{atoms/mol} \]

Final Answer