In experimental Procedure, Part A.1. For preparing a set of standard solutions of FeNCS2+, the equilibrium molar concentration of FeNCS2+ is assumed to equal the initial molar concentration of the SCN- in the reaction mixture. Why is this assumption valid?A) The high concentration of the iron ion ensures that the reaction is favored to go to the rightB) The high concentration of the SCN- ion ensures that the reaction is favored to the rightC) The low concentration of the iron ion ensures that the reaction is favored to go to the rightD) This reaction will not reach equilibrium

According to Le Chateliers principle, when a constraint such as a change in concentration, pressure or volume is imposed on a chemical system in equilibrium, the system will readjust itself in order to annul the constraint. This is done by shifting the position of equilibrium, either to the left hand side or the right hand side depending on the requirement of the system based on the imposed constraint. Equilibrium his now reestablished in the system as a result of this readjustment.

Since there is a high(excess) concentration of iron in the system, it can be safely assumed that the equilibrium concentration of the FeNCS2+ is equal to the initial concentration of SCN- ion present. This implies that the equilibrium position moves towards the right hand side according to Le Chateliers principle.