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Investigate the factors, which affect the rate of decomposition of Hydrogen Peroxide.

Extracts from this document...

Introduction

Investigating Reaction Rates Task Investigate the factors, which affect the rate of decomposition of Hydrogen Peroxide. Introduction The factors that could have affected the rate of the decomposition of Hydrogen Peroxide were: 1. The temperature of the Hydrogen Peroxide, H2O2 because, as I increase the temperature, the particles gain energy and move around more quickly. Therefore, more collisions occur between the particles in a given time. These collisions are also harder. It is the collisions between the particles that allow them to react, the more collisions between the particles in a given time, the faster the reaction. This is called the Collision Theory and applies to all reactions. 2. The concentration of the H2O2 because, as the concentration increases, there are more particles in a given volume of solution and therefore more collisions in the given time. 3. The particle size of the catalysts, Manganese Oxide and the enzyme Catalase found in yeast because, as the size of the particles decrease, their surface area increases. This means that the particles in the solution will have more area of catalyst to react with, meaning more useful collisions will take place. I chose to investigated the affect of the temperature of the solution, H2O2 on the rate at which it decomposes, because I thought that out of the three possibilities, temperature would have the greatest effect on the results. Prediction Hydrogen Peroxide, H2O2, decomposes into water and oxygen. This reaction takes place slowly, but can be speeded up by adding a catalyst. A catalyst is a substance, which speeds up a chemical reaction and remains chemically unchanged at the end of the reaction. Many substances can be used as catalysts, but each reaction tends to have only a few specific catalysts. Catalysts work by loosening the reaction bonds in the reactants allowing the reaction to run more quickly and easily. This weakening of the reaction bonds means that a lower activation energy, EA , is required to break the bonds. ...read more.

Middle

I therefore decreased the amount of oxygen to be given off to 30cm3. The trend that appeared in all the results that I gathered was that as the temperature increased, the time taken for the reaction to take place, the reaction rate, decreased. This matched my earlier prediction and gave me an indication that I would get the trend in my results that I expected and that I was carrying out the experiment in the correct manor. Apart from those alterations mentioned above, I decided that the rest of the experiment was a suitable and effective as possible and is therefore included in my final method in the same format as explained above. Method I set up the equipment as planned and shown in the diagram on page 3. I carried out the experiment as planned, with the exception of the quantities of the products and volume of gas to be collected. I heated 20cm3 of H2O2 with a concentration of 2.5vol, on a Bunsen burner to 60?C. I reduced the vol. of the H2O2 because of the results I got from my preliminary work. I concluded that the concentration was too high and was consequently causing the reaction to happen too quickly. I also decided to change the range of results that I gathered. Instead of going all the way up to 80?C, as in my preliminary work, I decided to stop at 60?C. Once it was heated to the correct temperature, I took it off the heat, added 1g of Manganese Oxide, put the bung in the top of the flask (as shown in the diagram), and started the stop-clock. I did all this as fast as possible, so that I didn't loose any of the oxygen already given off, which would make my results inaccurate. When I had collected 30cm3 of Oxygen in the measuring cylinder, I stopped the clock. It was also from the results of my preliminary work, that I reduced the volume of gas that was collected to only 30cm3. ...read more.

Conclusion

This problem could have been overcome by dissolving the yeast in water before adding it to the Hydrogen Peroxide. The entire solution of yeast and water could be added and the water would have the catalase dissolved in it already, meaning that the reaction can start immediately. By overlooking this problem, all these results were unreliable, although the results gathered when using Manganese oxide were very effective. My preliminary work was particularly useful as it allowed me to identify the appropriate quantities and concentrations of the reactants, which meant that I got sensible and useful results. In the preliminary work, several of the results were too quick to time, but this was rectified and the final results were successful because of this. To achieve better results in the future, I would try and gather all the results on the same day, or at least ensure that the same equipment and batches of chemicals are used in each trial. This would ensure continuity in the results that I didn't have in this investigation. If I repeated this experiment again, I would aim to gather more results at different temperatures. This would give me more points to plot on a graph. This would be very useful as several of the graphs that I produced for this investigation were only drawn from several points as the remainder were declared to be anomalous. As a further line of investigation, I would like to investigate the effect of different catalysts on the reaction with H2O2, at various temperatures. I would perform exactly the same experiment but using a different catalyst. This would mean that I could compare the results that I got from this investigation into manganese oxide and catalase with that of other catalysts. This would also either support or disagree with my prediction that there are only a few specific catalysts that will catalyse a certain chemical. Investigating Reaction Rates. -Created by Laura Mary Evans - 1 - ...read more.

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