Question

How would the absorbance of the standard solution have been affected if 0.00050 M NaSCN had been used in place of 0.00040 M NaSCN?

Answer 1

If iron(III) was the limiting reagent, would there be any difference in A?

Answer 2

the limiting reagent is the SCN

Answer 3

If I am determining the amount of iron(III) with thiocyanate, then I want iron to be the limiting reagent. If I am determining SCN^-, I want the limiting reagent to be SCN^-. Of course you may be doing something different but your post provides none of that information.