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HOW CONCENTRATION AFFECTS THE RATE OF REACTION

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Introduction

HOW CONCENTRATION AFFECTS THE RATE OF REACTION Research Question: How does the concentration of the substrate Hydrogen Peroxide affect the rate at which the reaction takes place with the enzyme yeast to reach the top of the test tube? Variables: Dependent variable: the rate at which the reaction of Hydrogen Peroxide with yeast reach the top of the test tube. Independent variable: concentration of the substrate Hydrogen Peroxide. Constant variable: the amount of enzyme yeast and Hydrogen Peroxide. Hypothesis: As the concentration of Hydrogen Peroxide increases, the rate of reaction with yeast will also increase and therefore, the faster the reaction will reach the top of the test tube. This is predicted because if the concentration of a substrate is increased in a solution with a fixed concentration of enzyme, substrate-active site collisions will take place more frequently and the rate at which the enzyme catalyzes its reaction will increase. Apparatus and chemicals: * Yeast (solid) * Hydrogen Peroxide of concentrations: (i) 0% (ii) 3% (iii) 6% (iv) 10% (v) 15% * Distilled water * Test tubes (same sizes) * Test tube holder * Beakers * Spatula * Electronic weighing scale (grams) * Petri-dish * Measuring cylinder * Stopwatch * Safety goggles Method for controlling variables: * Use a measuring cylinder to measure out 3ml of Hydrogen Peroxide for all the concentrations by keeping the cylinder at the eye level to get an accurate measurement (make sure the safety goggles are on). ...read more.

Middle

Slightly warm. Had slight odour. Yeast pieces expand and dissolve. 6% 07.28 05.31 05.30 Fast reaction. Lot of white froth appears. Colour changes to white. Slightly warm. Smelt like champagne. Yeast pieces expand and dissolve. 10% 05.19 04.75 04.93 Faster reaction. Lot of white froth appears which rapidly increases and gets out of the test tube. Colour changes to white. Quite warm. Stronger smell of champagne. Slight smoke appeared. Yeast pieces expand and dissolve. 15% 04.54 04.54 4.54 Fastest reaction. Lot of white froth appears which rapidly increases and most of it gets out of the test tube. Colour changes to white. Quite warm. Stronger smell of champagne. Could see more smoke. Yeast pieces expand and dissolve. From these results I was able to plot a graph for the time taken for the reaction to reach the marked point on the test tube against concentration of Hydrogen Peroxide: Data processing: Concentration of Hydrogen Peroxide (%) (� 0.5) Average time taken (sec) (� 00.005) Percentage uncertainty (%) (� 0005) 0% 00.00 + 00.00 + 00.00 3 = 00.00 (00.001 + 00.001 + 00.001) x 100 0.00.00 = 0.000 % 3% 13.09 + 12.85 + 12.97 3 = 12.97 (00.001 + 00.001 + 00.001) x 100 0.12.97 = 0.023 % 6% 07.28 + 05.31 + 05.30 3 = 05.96 (00.001 + 00.001 + 00.001) ...read more.

Conclusion

This is a random error. * Another error would have occurred while pouring the Hydrogen Peroxide into the test tube from the measuring cylinder since not all the amount would have been poured in. some amount could have remained in the cylinder while some amount could have dropped out of the test tube while transferring. Improvements: * This experiment could be improved in a number of ways. It could be repeated more then three times to get a more accurate result. A better overall result would be obtained by repeating the experiment more times because any errors in one experiment should be compensated for by the other experiments. * Using more concentrations of Hydrogen Peroxide would have produced a better looking graph and I would have liked to use concentrations higher than 15% to extend the graph so that the maximum possible rate of reaction could be reached. * The problem of starting the stopwatch at the same time while pouring the Hydrogen Peroxide could be overcome by getting another person to start the stopwatch when the Hydrogen Peroxide was poured into the tube. * A more accurate electronic weighing scale which gives its answer in three decimal places would give a better result. ?? ?? ?? ?? Amrita Raichura 11T Biology: Lab Report ...read more.

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