Answer : The number of moles of oxygen atoms are 135 moles.
Explanation : Given,
Moles of [tex]Fe(NO_3)_3[/tex] = 15.0 mole
The given chemical formula is, [tex]Fe(NO_3)_3[/tex]
By the mole concept:
In [tex]Fe(NO_3)_3[/tex], there are 1 mole of iron (Fe) atom, 3 moles of nitrogen (N) atoms and 9 moles of oxygen (O) atoms.
As, 1 mole of [tex]Fe(NO_3)_3[/tex] contains 9 moles of oxygen atoms
So, 15.0 moles of [tex]Fe(NO_3)_3[/tex] contains [tex]15.0\times 9=135[/tex] moles of oxygen atoms.
Hence, the number of moles of oxygen atoms are 135 moles.