Work to be done:
- By experiments find out how chemical equilibria works. Chemicals and setup:
- Two beakers
- Five test-tubes
- Kaliumtiocyanat, KSCN
- 0.002M Kaliumtiocyanatsolution, KSCN + H2O
- Dinatriumfosfat, Na2HPO4
- 0.002M Iron ( III ) nitratesolution, FeNO3
- 0.2M Silvernitratesolution, AgNO3
Lab
One test-tubes is filled half of distilled H2O ( A ) and another with kaliumtiocyanatsolution ( B ) . Both solutions are colourless. Solution ( B ) contains SCN- . I add five beads of Fe ( III ) nitratesolution to both test-tubes and the kaliumtiocyanatsolution turns dark-red. The account is that there has been a reaction in solution ( B ) , Fe3+ + SCN- FeSCN2+ , where FeSCN2+ has a dark-red colour. Lab 2 The solution in test-tube ( B ) is placed in five other test-tubes. I will now execute four different experiment and so compare with the original solution, and therefor I label the test-tubes a, B, degree Celsius, vitamin D and e.In test-tube ( a ) I add some KSCN ( Adams ) and therefor raise the concentration of SCN- in the solution. The seeable alteration is that the solution bend darker red. And since FeSCN2+ is ruddy, the decision 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 a 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- a 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- a FeSCN2+, the reaction is to the left.
Conclusion
In the reactions above I have changed the equilibrium by changing the concentration of different substances.
