Answer:
12 molecules of NaCl
Explanation:
The term "unlimited supply of NaOH" means that NaOH is the reactant in excess hence FeCl3 is the limiting reactant that controls the amount of product formed.
Thus;
From the balanced reaction equation;
1 molecule of FeCl3 yields 3 molecules of NaCl
Hence;
4 molecules of FeCl3 yields 4 * 3/1 = 12 molecules of NaCl
