Final answer:
The equilibrium concentration of FeSCN2+ is determined by the initial concentration of the limiting reagent, which is SCN-, and is approximately equal to 0.000705 M assuming complete reaction and negligible volume change.
Step-by-step explanation:
The question involves calculating the equilibrium concentration of FeSCN2+ when equal volumes of Fe3+ and SCN- are mixed.
To find the equilibrium concentration of FeSCN2+, one must apply the principles of chemical equilibrium, taking into account the initial concentrations of reactants and the stoichiometry of the reaction.
Assuming that the reaction goes to completion due to the limiting reagent, the concentration of FeSCN2+ at equilibrium would be governed by the initial concentration of the limiting reagent. In this case, since SCN- has a much lower molarity, it will be the limiting reagent.
Therefore, the concentration of FeSCN2+ at equilibrium will be approximately equal to the initial concentration of SCN-, which is 0.000705 M, provided that the volume change is negligible and the reaction goes to completion.