Results: The first time I did this experiment I used 1g of Manganese Oxide, which with the High concentration produced enough gas to blow the end of the syringe. Because of this I had to compromise on 0.2g as it gave a good compromise between a good reaction that was relatively quick but also not too slow. With the volume of liquid I had no problems as I started with 50ml and this turned out to be appropriate. My results were read by the amount of gas collected over an amount of time. As I was working by myself this method was not only more practical but easier as well as some experiments would accelerate very quickly so it was hard to read off the value in time. By this method I had plenty of time to put the bung on and take the reading easily. The reason I chose 10secs to be my reading is that it showed the initial rate of reaction, which was the part of the reaction that is mainly affected by concentration. Also I found that if I used 20secs as my reading the gas syringe would fill up too much and fall off on the higher concentrations.
Having done the second experiment with a different batch of Hydrogen Peroxide I concluded that the second batch of Hydrogen Peroxide was less concentrated than the first and thus the results were lower.
Errors:
- The first error in my experiment is that the measurement of my Manganese Oxide I found sometimes to be inaccurate as when it was emptied into the conical flask not all the contents of the paper fell off and thus the reading was affected.
- Another error of my experiment was that I measured both the substances in the same measuring cylinder, so when I made a mistake in measuring I had to redo the whole tube.
- Also I believed that the second batch that I used to do the second set of experiments was of a weaker concentration than the first batch. This lowered my results and thus affected the average.
Modifications
& Improvements:
- In the real coursework I will use a more accurate method of measuring the amount of Manganese Oxide added to the Hydrogen Peroxide. The way I will do this is by weighing the paper after the Manganese Oxide has been added to make sure that all the Manganese Oxide has been deposited.
- Also I will use two measuring cylinders instead of one, for not only more accuracy but also to not have to pour away the mixture if I add too much of one substance.
Conclusion: Having studied my results and reading over my recordings the experiment has led me to believe that my hypothesis was correct. As the higher the concentration of the acid, the quicker the reaction rate was. For instance a concentration of 1M produced 53ml of Oxygen in 10secs, whereas a concentration of 0.4M only produced 11ml. This means that in the real experiment I will be able to write a correct hypothesis, as I will have already proved it once, and with the other information collected from the coursework the hypothesis should show true as long as the actual results are reliable.
Investigation of the effect of the concentration of hydrogen peroxide on the rate of reaction of its decomposition in the presence of Manganese (IV) Oxide catalyst
What is the reaction?
Hydrogen Peroxide decomposes in the presence of manganese (IV) oxide to produce water and oxygen, as shown below.
Mn (IV) oxide
2H2O2(l) 2H2O(l)+O2(g)
Hypothesis.
Having already tested this theorem I predict that the rate of reaction will increase as the concentration of the Hydrogen Peroxide increases.
Procedure.
For this experiment it was essential that the affecting factors of the experiment were kept constant. The reason for this is that as I was measuring the rate of the reactions the results could be easily changed by even a slight fluctuation in temperature, thus everything was kept constant except the concentration of the Hydrogen Peroxide. The way I kept the temperature constant in the experiment was by carrying out all the experiments in the same double period. This way the temperature could not be changed by the temperature at that time of day because the trial was carried out in the same double period. The other main constant to be kept was the volume of the Manganese Oxide and Hydrogen Peroxide. This was done by only accepting measurements for the Magnesium to within 0.01 of a gram, this accuracy proved problems in the first planning experiment and affected the readings so therefore in the coursework it was made sure that this hitch was changed to ensure that the optimum data were collected. This ensured accuracy and reliable readings. With the Hydrogen Peroxide I measured the water and the Hydrogen Peroxide in different cylinders in order to ensure that if I added too much of one substance I did not have to throw the whole batch away. This was done by using two smaller cylinders to measure the liquid and then a larger one to add the liquids together and pour. The reason for this is that the two smaller cylinders were very hard to pour simultaneously into the conical flask, so they were both poured into one cylinder for easier pouring. All these factors will ensure a fair test the highest extent possible.
Apparatus: Boss Head
Clamp
Gas Syringe
Measuring Cylinder X2 (50ml)
Measuring Cylinder (100ml)
Conical Flask (150ml)
Beaker (250ml)
Retort Stand
Hydrogen Peroxide (Irritant, Harmful if swallowed)(1M)
Manganese Oxide (Irritant, Harmful if swallowed)
Water
Safety Goggles (Required as Hydrogen Peroxide is irritant and can cause permanent damage)
Lab Coat (in order to prevent clothes from becoming dirty and being corroded)
In the experiment safety had to be kept at all time in order to make sure the test was of no danger to ourselves.
Diagram:
Diagram will be drawn here by hand but cannot be drawn by computer
Method: The apparatus was set up as above with the bung not yet attached to the conical flask. For the first experiment 50 ml of Hydrogen Peroxide was measured into a beaker and placed into the conical flask. 0.2g of Manganese Oxide was then measured out onto a piece of paper and weighed to ensure accuracy. The Manganese Oxide was then placed into the conical flask, which was then immediately sealed with the bung, and the stopwatch was started. The amount of air displaced was also measured when the bung was fastened to the conical flask in order to subtract from the final reading. After 10 seconds the volume of air produced by the reaction was measured and the conical flask was detached and cleaned. This process was repeated seven times, except with different concentrations, 1M, 0.9M, 0.8M, 0.7M, 0.6M, 0.5M, and 0.4M. This was to obtain a good set of results by taking a range of different readings. The concentration however was changed in all these experiments to observe the affect of it on the rate of the reaction. Experiments were done with Hydrogen Peroxide 50-0 Water, Hydrogen Peroxide 45-5 water, 40-10, 35-15, 30-20, 25-35, 20-30 (these are the ratios of Hydrogen Peroxide-water). In the molars this is 1, 0.9, 0.8, 0.7, 0.6, 0.5, 04. The whole set of experiments were then taken again twice in order to obtain a good average.
Results Having already obtained a good set of values from the trial experiment with the volume of liquid I had no problems as I started with 50ml and this turned out to be appropriate. My results were read by the amount of gas collected over 10 seconds. The reason I chose 10secs to be my reading is that it showed the initial rate of reaction, which was the part of the reaction that is mainly affected by concentration. As I was working by myself this method was not only more practical but easier as well as some experiments would accelerate very quickly so it was hard to read off the value in time. By this method I had plenty of time to put the bung on and take the reading easily. Also I found that if I used 20secs as my reading the gas syringe would fill up too much and fall off on the higher concentrations. The results on the table below show. The higher concentrations
The higher concentrations have evolved more gas. The reason for this is that there is more collisions due to the higher amount of particles that will react contained within the liquid. This can easily be shown on a diagram like below.
As you can see if there are more collisions there is more gas evolved in a short amount of time, as the time in which it takes certain particles to collide is quicker. However this does not change the amount of gas evolved over a long time as no matter how concentrated the mixture is after a long period of time it will have all reacted and overall will have produced the same amount of gas due to similar volume of the two mixtures. This is why we took the reading at ten seconds, as it would show the real difference between the concentrations.
Errors:
- The first error in my experiment is that the measurement of my Manganese Oxide I found sometimes to be inaccurate as when it was emptied into the conical flask not all the contents of the paper fell off and thus the reading was affected. This was the same as the errors I found in the trial, so after the experiment I weighed the paper to make sure that all the Manganese Oxide was deposited. If it was not then I repeated the experiment again to get better results.
- Also due to the fact that I was by myself I was often in a hurry and as a result of this I often spilt the apparatus as I was in such a rush to do everything in time. Due to this I had to start three experiments again.
Modifications:
- One modifications I could possibly make is that I would do it in a pair
As having done a trial experiment there was nothing really that I could obtain better by using a different method therefore the only modification would be to do it in a pair, as it would be easier to obtain the data and carry out the experiment.
- Another is that I would measure the weight of the piece of paper after the experiment to make sure all the Manganese Oxide had been deposited. If it had not I would repeat the experiment.
Conclusion: Having studied my results and reading over my recordings the experiment has led me to believe that my hypothesis was correct. As the higher the concentration of the Hydrogen Peroxide, the quicker the reaction rate was. For instance a concentration of 1M produced 51ml and 38ml of Oxygen in 10secs, whereas a concentration of 0.4M only produced 10ml and 14ml. This clearly shows that the higher the concentration of the Hydrogen Peroxide the higher the reaction rate.
