Determination of an Equilibrium Constant
Autor: Aaron Cotton-Betteridge • March 21, 2016 • Study Guide • 332 Words (2 Pages) • 913 Views
Lab 5 -The Determination of an Equilibrium Constant
Experimental Data and Calculations:
Part I
Beaker | [FeSCN2+] | Absorbance |
1 | 1.6e-4 | 0.624 |
2 | 1.2e-4 | 0.475 |
3 | 8.0e-5 | 0.310 |
4 | 4.0e-5 | 0.153 |
Part II
Beaker | Absorbance (y) | [FeSCN2+] at equilibrium (x) |
A | 0.222 | 5.52e-5 |
B | 0.305 | 7.63e-5 |
C | 0.369 | 9.25e-5 |
To calculate for x ([FeSCN2+] at equilibrium) I rearranged the equation so that we are solving for x which gave me . To calculate the [FeSCN2+] at equilibrium for Beaker A I divided the difference of absorbance and the y intercept by the slope. .[pic 1][pic 2][pic 3]
Next, I calculated the initial concentration of each reactant in each of the three beakers so I could use an I.C.E chart to find for the equilibrium of each reactant and therefore the overall equilibrium constant for the reaction. To find the initial concentration I multiplied the concentration of the reactant by its volume in the beaker and divided that by the total volume in the beaker.
Example:
[pic 4]
Because I now knew the initial concentration for each reactant and x, I set up an I.C.E chart for each of the three beakers to solve for its equilibrium concentration. Because the reaction was going to the right (Fe3+ and SCN- were reacting to form FeSCN2+) I could minus the change in concentration (x) previously solved for, from their initial values of reactants and add that change in concentration to the products on the right.
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