Chem 216 Lab T/Th 8-10:50
January 31, 2013
Kinetics of H2O2 Decomposition
When measuring the rate of a reaction one can measure the rate at which one of the product appears or the rate at which the reactants disappear. The actual rate of a chemical reaction however is dependent on two things; the temperature the actual experiment is performed at, and the concentration pertaining to the reactants. The rate of a reaction more often than not depends on the concentration of one or all the reactants being used in the chemical reaction. This relationship that shows dependence can be expressed mathematically by the rate law, this can not be determined by just looking at a chemical equation it has to be determined experimentally as done in this experiment. In this experiment we will be looking at the rate of the decomposition of hydrogen peroxide, which yields liquid water and gaseous oxygen.
2H2O2 (aq) 2 H2O(l) + O2(g)
In this chemical reaction we will be examining the rate at which the product appears, in this case the rate at which oxygen gas is produced. This experiment will be performed more then once at different concentration levels to see how the rate of a reaction changes as the one changes the concentration levels. For this experiment we will also be using a catalyst to speed up the production of oxygen gas. The catalyst being used will be iodide ions, which will be introduced into the actual reaction through a mixture of potassium iodide, KI.
Once all the reactions are complete the rate will be found by using the rate law, which shows the dependence of the rate of the reaction of both the iodine and the hydrogen peroxide.
For this experiment we had to work in pairs. First we assembled an apparatus with a flask, buret and a leveling bulb all attached with plastic tubing. Fill the plastic tubing with room temperature water through the leveling bulb until both are full. The leveling bulb was placed close to the top of the buret so that as the water level rose and fell we could adjust the bulb accordingly. We also had to ensure that there was no air bubbles trapped in the tubing so that it wouldn’t affect the volume reading in our experiment. Next we connected a 250 ml flask to the plastic tubing with a stopper on the end so we could begin our experiments soon. Lastly on the assembly of the apparatus we had to check to ensure it was leak proof so no gas/liquid would escape.
Next we began to perform the experiment. First we added 10 ml of 0.10M KI and 15 ml of distilled water into our flask. Next we added 5 ml of 3% H2O2 into our flask and then stoppered the flask as quickly as possible. While the reaction was occurring one person had to swirl the flask, monitor the time and record the time intervals while the other person had to monitor the amount of oxygen produced to lower the water level and adjust the leveling bulb to ensure that the level of water in the buret was equal to that of the leveling bulb. The timer was started after there was enough gas produced to lower our waters volume by 2ml and then recorded at 2 ml intervals until 14 ml of oxygen had been accumulated in the buret. This process was done twice.
Once the first experiment was complete we rinsed our flask with distilled water and repeated the same process except this time using 10 ml of .10 M HCL but only 10 ml of distilled water and 10 ml of 3% H2O2. Once the content were in the flask we quickly stoppered it and recorded the times as done in experiment one. This was done twice as well.
Lastly for experiment three we rinsed the flask once again with the distilled water and then began to fill it with this time 20 ml of the .10 M KI and only 5 ml of distilled water and 5 ml of H2O2 and then just as in experiment one and two we stoppered it quickly and then recorded times as done in the previous two experiments. This process was done twice just as it was...