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An investigation to find the rate of reaction between hydrogen peroxide and Catalase as the concentration of hydrogen peroxide is changed.

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Introduction

The Decomposition of Hydrogen Peroxide by Catalase The Decomposition of Hydrogen Peroxide by Catalase Aim: An investigation to find the rate of reaction between hydrogen peroxide and Catalase as the concentration of hydrogen peroxide is changed. Introduction: Enzymes are biological catalysts. They therefore increase the rate of reaction by decreasing the activation energy required for that reaction. The catalyst itself is not changed in anyway in the reaction or breakdown. Its main task is to decompose hydrogen peroxide into its elements, oxygen and hydrogen. Fig 1. Shows lowered activation energy with use of enzyme Enzymes are globular proteins which are polymers made up of monomers called amino acids and form a three-dimensional shape. These shapes are determined by the tertiary structure of the proteins. Enzymes have an active site. This is an area on the surface where the substrate molecules combine with the enzyme. The shape of the active site is very important because it complements the shape of the substrate. Enzymes have active sites that are specific to a substrate molecule. This means it is only able to catalyse particular reactions. Catalase is specific to hydrogen peroxide. Therefore I will be using this substrate throughout my investigation. Hydrogen Peroxide is a viscous liquid that has strong oxidising properties. It is water soluble and is commercially used in disinfectants and germicides. Hydrogen peroxide often decomposes exothermically into water and oxygen gas spontaneously: 2H2O2 (aq) --> 2H2O (g) + O2 (l) + Energy Hydrogen peroxide can be decomposed by many organic compounds like dirt, but Catalase has a main function of removing toxic by-products of metabolism. ...read more.

Middle

* 0.6M (6ml Hydrogen peroxide/4ml Distilled water) * 0.4M (4ml Hydrogen peroxide/6ml Distilled water) * 0.2M (2ml Hydrogen peroxide/8ml Distilled water) * 0.0M (0ml Hydrogen peroxide/10ml Distilled water) Equipment list: Hydrogen Peroxide (10 Vol) Catalase (100%) Delivery Tube Burette Clamp and stand Distilled Water Timer Water Bath Beakers Thermometer 25ml Conical Flask Pipette Goggles Lab Coat Gloves Diagram: Method: 1) Switch on the bath at 30�C (confirm Temperature with Mercury thermometer) 2) Set up the Equipment as show in the diagram above. 3) Create Catalase solution by adding 0.32ml of Catalase to 1.68ml of distilled water in a 10ml beaker. (Use 1ml pipettes to measure these values. Note: Use and label two different pipettes for each solution). 4) Create Hydrogen Peroxide solution as shown above in concentration section. (Note: use 10ml pipettes, separate pipettes for each solution). Pour the hydrogen peroxide solution into the 25ml conical flask. 5) Pour the Catalase into the flask and place the stopper on the top, and start the timer. 6) Record Results for every 60s Results: H2O2 (ml) H2O (ml) Catalase (ml) Vol. of Oxygen (ml) Time (s) 10 0 2 30 10 8 2 2 45 10 6 4 2 39 10 4 6 2 22 10 2 8 2 7 10 0 10 2 0 10 The problem encountered in this preliminary test was the high concentration on Catalase. It should now be changed to a lower concentration for a re-test. Unfortunately the reactions were so fast that a lot of the oxygen was released before the bung could be placed on the conical flask. ...read more.

Conclusion

Evaluation: Criticisms of the method: * The main problem with the method stated earlier is that the bung is not replaced earlier enough when the concentration of the hydrogen peroxide is too high. The problem is that too much oxygen is leaked before that bung is put back to seal the conical flask. * Hydrogen peroxide is measured in Vol's not moles. This could cause the results to be inaccurate as to the usual behaviours of a 1 mole concentration. * When using a pipette some times an air bubble may get in the way, and it isn't always possible to remove them, like when measuring hydrogen peroxide where there are health risk precautions that need to be taken. * The timer may have been started a little late due to human reaction time, and also in the cases where the concentration of hydrogen peroxide is high there wasn't always enough time to start the timer and put the bung on the top of the conical flask at the same time, this caused some timing errors. Improvements: * Clean all equipment that needs to be used thoroughly before use. * More repeats need to be taken to obtain more accurate results. * Investigate with more variables like, the concentration of Catalase or temperature. Percentage error: Percentage error = (error / measurement taken) x 100 Maximum error calculated * Thermometer - error = � 0.05�C (0.05 /30) x 100 = 0.1667% * Burette - error = � 0.1ml (0.1/14.4) x 100 = 0.694% * Pipette - error = � 0.1cm3 (0.1/0.2) x 100 = 5% * Timer - error = � 0.005s (0.005/60) x 100 = 0.0083% Total = 5. ...read more.

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