[CHM 112] Aqueous Equilibrium Standardization Plot

[Andrew J. Pounds]

Class -- I have placed an example of a standardization plot (yours will 
have different values) for the Aqueous Equilibrium lab on the class 
website...

http://theochem.mercer.edu/chm112/aqequil.png

Here is the reaction that we are studying...

Fe^3+ (aq) + SCN^- (aq) -> FeSCN^2+ (aq)

This is a NET IONIC reaction.  The iron (III) and thiocyanate ions are 
delivered to the solution by the strong electrolytes Fe(NO_3 )_3 and 
KSCN.  You will therefore use the volumes and concentrations of those 
solutions, as well as the volume of the nitric acid, to compute the 
initial concentrations of the iron (III) and thiocyanate ions.

For the first part of the reaction where you are computing the standards 
for your plot, the iron (III) concentation is MUCH larger than that of 
the thiocyanate, so you will be, according to LeChatelier's principle, 
be driving the equilibrium all the way to the right.  That means that 
initial concentration (after computing you dilutions) of the FeSCN^2+ 
ion is the same as the SCN^- ion.

This will emphatically not be the case for the second part of the lab.  
I will provide more information on that later -- but you should have 
enough now to go ahead and build your calibration plots before class 
tomorrow.


-- 
*/Andrew J. Pounds, Ph.D./*
/Professor of Chemistry and Computer Science/
/Director of the Computational Science Program/
/Mercer University/
/1501 Mercer University Drive, Macon, GA 31207 /
/(478) 301-5627/
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