# Question #3c610

The answer is $11.5$ moles of $C o$.
We know that 1 mole of any substance has $6.022 \cdot {10}^{23}$ atoms (or, depending on the substance, molecules); this is known as Avogadro's number.
Since we were given the number of $C o$ atoms, we can calculate the number of moles to be
$\frac{1 m o l e C o}{6.022 \cdot {10}^{23} a t o m s C o} \cdot 6.94 \cdot {10}^{24} a t o m s = 11.5$ moles
You could try and estimate this number before doing any calculations by taking into account the fact that the number of atoms given is at least 10 times greater than Avogadro's number (${10}^{24}$ vs. ${10}^{23}$), so the number of moles should be at least 10.