You will use a large excess of fe+3 ion, which will drive the reaction to completion. thus, you can assume that the final fescn+2 concentration is equal to the concentration of kscn added, as the kscn is the limiting reagent, in the total volume of the solution. you must test each solution as it is made; therefore, you must plan out ahead of time with your partner how you will accomplish this in an organized and expedient way.