Question

How many moles of copper are equivalent to $3.44\cdot {10}^{23}$ atoms of copper ?

Answer 1

First you need to find the conversion factor. We know that $1$ mol. contains Avogadro's number of atoms and therefore our conversion factor will be:
$1mol.=6.02\times {10}^{23}$ atoms.
$3.44\times {10}^{23}$ atoms $\times \frac{1mol.}{6.02\times {10}^{23}atoms}$
$3.44\times {10}^{23}$ atoms $\times \frac{1mol.}{6.02\times {10}^{23}atoms}$
$0.571mol$