chem 1A disc determ of equil spectro

chem 1A disc determ of equil spectro - The way we found K...

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Janice Oldham Chem Lab W-1pm Dennis 5 December 2007 Discussion: Determination of an Equilibrium Constant Using a Spectrophotometer In part 1 of this experiment we measured the absorption of Fe(SCN)2+ using a spectrophotometer. We used a mixture of Fe(NO3)3, KSCN, and HNO3. The concentration of Fe(SCN)2+ could then be determined using the molarity and total volume of the solution. Taking these results, we made a graph of the absorption versus the concentration and were able to find a line of best fit. We then used this equation to determine the experimental concentration of Fe(SCN)2+ in part 2. The main point of this lab appears to be to prove that the K is constant. We found the K constant to be an average of .2510 with a standard deviation of .1257. In part 2 of this experiment we used the same molecules, just different concentrations.
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Unformatted text preview: The way we found K for each solution was to find the initial concentrations of Fe3+, SCN-, and Fe(SCN)2+, then to determine x by using the equation for the trend line on our calibration graph. From there we found the final concentration or equilibrium concentration for each reactant and product by either subtracting or adding as appropriate. Finally we plugged the numbers to the equation like so: K = [Fe(SCN)2+ + x] / ([Fe3+ - x] * [SCN- - x]). The balanced equation for this experiment is Fe3+ + SCN- Fe(SCN)2+. Possible sources for error in this lab could have been variations in the actual concentrations of the substances. Because they were already prepared, there might have been different concentrations than what was given. Another source of error could have been the spectrophotometer and its accuracy....
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chem 1A disc determ of equil spectro - The way we found K...

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