Chemical Equlilbria Essay, Research Paper

Work to be done: *By experiments find out how chemical equilibria works. Chemicals and apparatus: *Two beakers *Five test-tubes *Kaliumtiocyanat, KSCN *0.002M Kaliumtiocyanatsolution, KSCN + H2O *Dinatriumfosfat, Na2HPO4 *0.002M Iron(III)nitratesolution, FeNO3 *0.2M Silvernitratesolution, AgNO3Lab: Lab 1 One test-tubes is filled half of distilled water (A) and another with kaliumtiocyanatsolution (B). Both solutions are colorless. Solution (B) contains SCN-. I add five drops of iron(III)nitratesolution to both test-tubes and the kaliumtiocyanatsolution turns dark-red. The explanation is that there has been a reaction in solution (B), Fe3+ + SCN- à FeSCN2+, where FeSCN2+ has a dark-red color. Lab 2 The solution in test-tube (B) is placed in five other test-tubes. I will now perform four different experiment and then compare with the original solution, and therefor I label the test-tubes a, b, c, d and e.In test-tube (a) I add some KSCN (cristals) and therefor raise the concentration of SCN- in the solution. The visible change is that the solution turn darker red. And since FeSCN2+ is red, the conclusion is that the solution contains more FeSCN2+.To test-tube (c) I add some FeNO3 and the concentration of Fe3+ is increased and the solution turns darker red à the concentration of FeSCN2+ is higher. Since no more SCN- has been added the ratio Fe3+ and SCN- must be in equilibrium. The solution now contains Fe3+, SCN-, FeSCN2+, NO3- and K+.To test-tube (d) I add five drops of silvernitrate, AgNO3, and the solution is turning brighter – the concentration of FeSCN2+ must decrease. There seems to be a fight about the SCN-ions, both Ag+ and Fe3+ want them, but the Ag+ions seems to win and form a salt, AgSCN, that is hard diluted in water. The effect is, as described earlier, that the concentration of FeSCN- has decreased and the color of the solution is lighter red. The reaction formula is Fe3+ + SCN- à FeSCN2+, the reaction is to the left and the reaction is reversible.In the last test-tube I add some dinatriumhydrofosphate, Na2HPO4, and the solution becomes colorless, there is no more FeSCN2+. The concentration of Fe3+ has decreased. In the reaction Fe3+ + SCN- à FeSCN2+, the reaction is to the left. CONCLUSION: In the reactions above I have changed the equilibrium by changing the concentration of different substances.