Looking back at the research question, the actual amount of reactant did not match the theoretical stoichiometric amounts according to the balanced equation, but the amount of catalyst matched the original value when uncertainty is taken into account. The percent yields for the reactants in the equation are very far from 100% yield. In the case of water, the percent yield came out to be meaning there were at least 2 times to 4 times more water than there should be. The percent yield of oxygen came out to be , around 2%, maybe higher considering uncertainty of what amount of oxygen there was suppose to be.
The reaction was incomplete and had to be stopped because of time, which explains the very high percent yield of the water and the very low percent yield of oxygen. The yield of the catalyst though, came out to a perfect , which means that including uncertainty, there was as much MnO2 that came out of the reaction as was put in the reaction. This proves that catalysts do not get consumed in the reaction, with added evidence that even though the reaction was incomplete, the catalyst was not affected and therefore is not a part of the products or reactants and is not consumed.
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Based on uncertainty analysis, I have a very low degree of confidence in the results regarding the reactants mainly because of procedural uncertainty. I have a strong degree of confidence in the result regarding the catalyst because of the small uncertainty. The method of the experiment resulted in a large degree of uncertainty in the results. There were two major sources of procedural uncertainty. The source that affected the data the most was due to the fact that because of time limitations, the reaction had to be cut short and stopped at around 10 minutes after the start of the reaction.
As a result, the reaction was incomplete, leaving un-reacted products and reactants that weren’t produced yet and therefore any measurement of the reactants, oxygen and water, was skewed. The direct result was the low yield of oxygen as the reaction was stopped before all the oxygen was produced leading to the low percent yield. Also, because the reaction didn’t use up all the hydrogen peroxide, the amount of “water” collected probably still had hydrogen peroxide, inflating the mass of the water leading to the high percent yield.
The second source of procedural uncertainty comes from the use of two devices to collect the catalyst after the reaction had been finished. The filter paper was used to filter the very fine MnO2 catalyst from the water and large chunks of catalyst got left behind in the flask and were massed separately from the catalyst on filter paper. In retrospect, the use of two devices to collect the catalyst was not a great idea as it added unnecessary uncertainty to the experiment. Two separate masses from MnO2 meant that the two amounts had to be added together, which also meant adding up the uncertainties.
The uncertainty the catalyst went from using only one mass, to by using two masses. Another minor source of procedural uncertainty was the catalyst that got left in the sample tray as the catalyst was being poured into the vial. That means that the amount of catalyst actually used in the reaction is slightly less than the amount measured out, recorded and used in the reaction. This is not so much of a worry because the amount of the catalyst that got left on the tray is miniscule and is too insignificant to be dealing with.
There are several things that can be done to improve the experiment and increase my degree of confidence in the results. Firstly, in the future, ample time should be allotted for the reaction complete. To increase my degree of confidence, I should use only the filter paper as the collection device for the catalyst will greatly decrease the uncertainty. To increase my degree of confidence, the sample tray should have been re-massed after the MnO2 was poured in the vial to ensure that the actual amount of catalyst is recorded.