# How many CO_2 molecules are there in 10.0 mol of carbon dioxide?

Exactly $10 \cdot {N}_{A}$ molecules.
Since there are $6.02 \cdot {10}^{23}$ molecules in a mole, in $10$ moles of carbon dioxide, there will be:
$10 \cdot 6.02 \cdot {10}^{23} = 6.02 \cdot {10}^{24}$ carbon dioxide molecules