Manganese oxide - Sample Essay
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. 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 a relatively short time. 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 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. Also as I used two smaller cylinders which allowed for more accuracy. All these factors will ensure a fair test the highest extent possible. Apparatus: Boss Head Clamp Gas Syringe Measuring Cylinder X2 Conical Flask Beaker Stand Hydrogen Peroxide (Irritant, Harmful if swallowed) 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 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 was measured and the conical flask was detached and cleaned. This process was repeated seven times, except with different concentrations. This was to obtain a good set of results.
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, . The whole set of experiments were then taken again twice in order to obtain a good average. 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. Concentration of Hydrogen Peroxide Displacement of air Volume of Oxygen produced In 10secs (1) Displacement of air Volume of Oxygen produced In 1’secs (2) 1 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.