So,
We want to find the number of moles of Fe(OH)3 produced from 5.0 moles of NaOH according to the reaction:
We can see that NaOH and Fe(OH)3 have a 3:1 ratio due to the reaction coefficients. This means that, per each mol of Fe(OH)3, 3 moles of NaOH react.
Using this proportion, we have:
Therefore, the answer is 1.7 moles of Fe(OH)3.