Determination of the Equilibrium Constant for a Chemical Reaction

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Equilibrium Molarity Fe3+ = (9.30 X 10-4mols Fe3+) 0.01 L

When all the equilibrium molarities are known for both products and reacts are known, the equilibrium constant can be found using:

Kc= =Kc= =111

Discussion:

In this experiment, the equilibrium concentration of the product was trying to be found and when found use that data to find the equilibrium concentration of the reactants. In order to then determine the equilibrium constant of the reaction. The experiment was done with different volumes of one of the reactants, HSCN, but the total volume of the solution and initial moles of the other reactant, Fe3+, stayed the same. In theory no matter how much of the HSCN you put as long as there were 10 ml of the solution, 5 of that being the Fe(NO3)3, and the concentration held constant than the equilibrium constant should be the same. The data collected in this report supports the theory with the equilibrium constant of each of the different solutions having relatively close equilibrium constants. Knowing the equilibrium constant of a reaction can then be used to find the concentration of any of reactants and products at equilibrium as long as the other 3 concentrations are known. This is useful because now instead of having to redo an experiment to solve for a different concentration in either the products or reactants, in can be solved using the same equilibrium constant and the known concentrations.

Error analysis:

In the experiment, the concentration of the indicator, H+, stayed the same because it caused such an insignificant change. If, however the it was large enough then the equilibrium constant would change for each different solution.

Post-Lab questions:

1. Yes, it my results prove the equilibrium concept because they show the forward and reverse reaction are equal in the point of equilibrium.

2. Kc = 124 = x = [FeSCN2+] =8.39 x 10-6 M ≈8.40x10-6

3.The concentration [FeSCN2+] would increase 10 fold as the reactant increases ten folds.

4. The concentration of H+ is constant because the change is so small that it does not affect the equilibrium constant enough, however it is not constant for all reactions because the concentrations may be large enough to change the equilibrium constant.