[CHM 112] labs

[Andrew Pounds]

On 07/13/2015 09:15 PM,  wrote:
> Dr. Pounds,
>
> I had a few questions regarding the labs. On the concentration effects 
> one, how to we find initial concentration of [I-]? All I have is the 
> concentration of H2O2 which is .2001 M and N2S2O3 which is .020 M that 
> was given. Should the concentrations be the same for all flasks?
>
The other concentrations were written on the autopipetters.  But the 
main one you need is the I- concentration.  You should be able to find 
it in the lab procedures.
> Part two asks for initial concentration of H2O2 and im guessing that I 
> would fill in .2001 M and then the time in seconds it took for the 
> solution to turn blue. And then calculate
> rate= -Delta H2O2/Delta temp right?
No.  The concentration needs to be the diluted concentration.  All of 
the volumes you used are found in the lab procedures.  As far as 
calculating the rate, I just sent out another e-mail that described how 
to do that.
>
> For lab two, the temperature effects one, we are given the KMnO4 has a 
> concentration of .0050 M, but how do we calculate the concentration of 
> MnO4-? After calculating that, we would fill in temperatures starting 
> from the room temp, all the way up to 50 degrees over the room temp 
> all in kelvin, find the difference in time and then just plug in my 
> concetration and change in temperature, correct?
>
>
Potassium permanganate is a strong electrolyte and completely 
dissociates.  The concentration of permanganate ion is thus equal to the 
concentration of potassium permanganate.  Fill out the temps as you 
described and then calculate the rates as I described in the previous 
e-mail.  Then make me a pretty graph to determine the activation energy.

-- 
Andrew J. Pounds, Ph.D.  (pounds at theochem.mercer.edu)
Professor of Chemistry and Computer Science
Mercer University,  Macon, GA 31207   (478) 301-5627

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