What does 2H2O represent?
2 molecules of water
6 atoms in total
6 atoms in total or 2 molecules of water
4 atoms in total or 2 molecules of water
2H2O has 6 atoms in total (4 atoms of hydrogen and 2 atoms of oxygen) or 2 molecules of water.
Find the total number of molecules and atoms in the reactants:
N2+3H2→2NH3