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-   -   Determining Initial and Equilibrium Concentration (Help ) (http://www.physicsforums.com/showthread.php?t=583120)

galaticman Mar2-12 01:17 AM

Determining Initial and Equilibrium Concentration (Help!!!)
 
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 Mar2-12 02:48 AM

Re: Determining Initial and Equilibrium Concentration (Help!!!)
 
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 Mar2-12 03:26 AM

Re: Determining Initial and Equilibrium Concentration (Help!!!)
 
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 Mar2-12 04:19 AM

Re: Determining Initial and Equilibrium Concentration (Help!!!)
 
It doesn't matter - if the solution is 2x10-3 M in NaSCN, it is also 2x10-3 M in Na+ and SCN-.

galaticman Mar2-12 12:01 PM

Re: Determining Initial and Equilibrium Concentration (Help!!!)
 
Ohhhh okay I got it then! Thanks!!!!!


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