As we have a large excess of one reactant (Fe3+), the reaction essentially goes to completion. Consequently, for the first week, and only the first week, of the experiment, the initial concentration of the SCN— reactant is equal to the equilibrium concentration of the Fe(SCN)2+ product. So, think about that and answer: if you have a large excess of Fe3+, what is your limiting reagent?
• A. Fe3+
• B. SCN—