# How many moles of NO_2 are there in 1.81 * 10^24 molecules of NO_2?

In finding the amount of moles there are, you first have to know what the mole is and what it represents. Avogadro's number is $6.022$x${10}^{23}$. That number can represent anything; in chemistry it often stands for atoms or molecules. In this question it represents molecules.
$1.81$x${10}^{24} \text{molecules}$ X 1mol$/$6.022$x$10^23"molecules"$=$3.00 mol