Procedure C:
Reaction:
K2CrO4 (aq) + HCl (aq) ←→ K2Cr2O7 (aq) + 3H2O (l)
Yellow colourless orange colourless
Procedure C:
Reaction:
Co2+ (aq) ←→ Co3+ endothermic reaction (+∆H)
Pink blue
2. The colour is Light Pink
3. when the solution is heated, this heat is treated as a product, thus the reaction moves towards the left to establish equilibrium. Purple is a colour between Pink and Blue, and when the solution is heated the colour changes to purple
Co2+ (aq) ←→ Co3+ endothermic reaction (+∆H)
Pink Purple *at equilibrium* Blue
4. When the solution is cooled down in an ice bath, the heat is lost and so the colour goes back to pink.
Conclusion & Evaluation
In conclusion, we can say that the Le Chatelier's Principle was applied very successfully in the above reactions. When there were more reactants added, the reaction shifted to the right thus having more products produced in order to re-establish its stable state at equilibrium. For example, when adding more HCl to K2CrO4 (aq) the colour changed to light orange, in other words shifting to the right and making more K2Cr2O7 so that equilibrium is re-established. The opposite happened when more products were added, the reaction shifted to the left, and more reactants were made to regain the state of equilibrium.
Overall, the experiment was successful on several levels. The was applied in every reaction of the reactions above and so in terms of design and method, nothing went wrong. The time specified was enough for the experiment to be done with no rush and to collect enough clear observations. the equipment was used very easily with no flaws or mistakes for example using the wells and labling them or using the bunsen burner to heat the solution up…etc. The progress of the experiment went smoothly and clear observations were collected. However, there were few limitations associated with the carrying out of the lab that can be either avoided or reduced in order for the experiment to be done easier. One limitation was the fact that the colors weren’t very clear, and it is hard for human eyes to distinguish between for example, light orange and dark yellow, and with only 10 drops of the solution, the color would not be clear enough to determine. This definitely will affect the observations negatively; because each colour stands for a specific species, if light orange was mistaken for dark yellow, then the observation of each species would be wrong; thus having wrong observations, means that the experiment was unsuccessful. One realistic solution would be to have a bigger well, so that more amount of each species is used thus making the change clear enough. In general, apart from those limitations the experiment was very successful.
