Question

A modern penny weighs 2.5 g but contains only 0.063 g of copper (cu). how many copper atoms are present in a modern penny?

Answer 1

The molar mass of copper is 63.546 g/mol. Therefore calculating for moles:

moles = 0.063 g / (63.546 g / mol) = 9.91 x 10^-4 mol

 

Using Avogadros number, we get the number of Copper atoms.

atoms = 9.91 x 10^-4 mol * 6.022 x 10^23 atoms/mol

atoms = 5.97 x 10^20 atoms

Answer 2

Answer:

$5.969\times 10^{20} atoms$ are present in a modern penny.

Explanation:

Mass of copper in modern penny = 0.063 g

Moles of copper : n

$n=\frac{0.063 g}{63.55 g/mol}=0.0009913 mole$

Number of copper atoms in 0.0009913 mole = n

$N=n\times N_A$

$N=0.0009913 mol\times 6.022\times 10^{23} mol^{-1}=5.969\times 10^{20} atoms$