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Determination of an Equilibrium Constant

Autor:   •  March 21, 2016  •  Study Guide  •  332 Words (2 Pages)  •  984 Views

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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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