Determining Initial and Equilibrium Concentration (Help!!!)

galaticman

1. The problem statement, all variables and given/known data
You are given the equation Fe³⁺ + SCN^- -> FeSCN^-
You are performing an experiment in which you are mixing Fe(NO₃)₃ and NaSCN. A table is given and I will only list the first sets of data because if i can figure out the process for the first one I can figure out the rest. The table is:

10 mL of 2.0x10^-3 M Fe(NO³)₃
2mL of 2.0x10^-3
Total Volume of Solution: 50mL

You are asked to to calculate the initial SCN^- concentration (M) as well as the equilibrium FeNCS²⁺ concentration (M)

I am just not sure how to go about doing that. Any help would be greatly appreciated!!!!!

NOTE: It also mentions that to assume all of the SCN^- is present as FeNCS²⁺ but I am pretty sure that this is irrelevant and is relevant to the later part of the lab

Borek

So, if I understand you correctly, you take 2 mL of 2x10^-3M solution of SCN^-, and you dilute it up to 50 mL (other solution doesn't matter at this moment)?

How many moles of SCN^- in these 2 mL? What is the concentration of the solution containing this amount of SCN^- in a 50 mL volume?

galaticman

Yup that is pretty much it except it is not just SCN it is NaSCN but Im not sure if that matters for the problem or not?

Borek

It doesn't matter - if the solution is 2x10^-3 M in NaSCN, it is also 2x10^-3 M in Na⁺ and SCN^-.

galaticman

Ohhhh okay I got it then! Thanks!!!!!