Answer
The answer is $111.6$ moles of Oxygen.
Work Step by Step
We can figure this out using simple mole ratios. According to the formula $Fe(NO_{3})_{3}$, 1 mole of $Fe(NO_{3})_{3}$ contains nine moles of oxygen (O) because the "3" outside the brackets is distributed to all of the terms inside the bracket and $3 \times 3=9$. So, 12.4 moles of $Fe(NO_{3})_{3}$ contains $111.6$ moles of O.
$12.4 moles\times 9 = 111.6 moles$
