Answer : The number '3' is a moles.
Explanation :
The given chemical formula is, [tex]3NO_2[/tex]
As we know that,
For 1 mole of [tex]NO_2[/tex], there are 1 mole of nitrogen and 2 moles of oxygen.
For 3 mole of [tex]NO_2[/tex], there are 3 moles of nitrogen and 6 moles of oxygen.
So, from this we conclude that the number '3' present before [tex]NO_2[/tex] represent the number of moles.
Hence, the number '3' is a moles.
