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The effect of concentration on the rate of reaction.

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The effect of concentration on the rate of reaction Aim: The purpose of this experiment is to find out if and how the concentration of a solution affects the speed of a chemical reaction. The reaction that I am going to study is magnesium and hydrochloric acid. Magnesium + Hydrochoric acid --> Magnesium chloride + hydrogen Mg(s) + 2HCL (aq) --> MgCl2 (aq) + H2 (g) Prediction: As we increase the concentration, the rate of reaction will also increases. The collision theory explains why the concentration affects the rate of a reaction. As the concentration of the acid increase, there are more acid particles in the same volume. Therefore, there is a great chance of acid particles colliding and reacting, with magnesium particles. So the rate of reaction will increase. Apparatus: * 20 cm of magnesium ribbon * scissors for cutting the magnesium ribbon * Emery paper to wipe off the deposit of magnesium oxide formed on the surface of the magnesium ribbon. * 2M of diluted hydrochloric acid * distilled water to dilute the acid * a stop watch to see how long it takes for the rate of reaction * 20 ml cylinders- to measure the amount of distilled water and acid. * Test tube racks- to hold the test tubes * 4 test tubes * ruler- to measure the length of the magnesium ribbon * pipettes Fair testing: Variable that ...read more.


This makes concentration of 1M of HCL. 6. Use the measuring cylinder, measure 2.5 of 2M HCL, then another 7.5 of distilled water (to dilute the acid). Pour them into another test tube. This makes the concentration of 0.5 M of HCL. 7. At the same time, put 4 pieces of 1.5 cm of magnesium ribbon, 1 each into each test tube. 8. Start the stopwatch straight away. 9. Measure the time taken for the magnesium to disappear in the solution, and it stopped bubbling and giving off hydrogen gas. 10. Record the result in a table. 11. Pour away all the solution in the test tubes and wash them. 12. Repeat steps 3-10 for 3 times, so we can obtain an average to ensure the accuracy of this experiment. Time taken for the magnesium ribbon to disappear (s) rounded up to nearest seconds. Concentration of HCL (M) 1st time (s) 2nd time (s) 3rd time (s) Average time (s) 2 15 18 19 17 1.5 37 52 40 43 1 110 80 90 93 0.5 330 380 420 378 Conclusion The graph agrees with my prediction. According to the set of results obtained, it shows that the more concentrated acid had a faster rate of reaction than the less concentrated acid. The line of best fit is a steep line. ...read more.


It was very hard to measure out the exact number of millilitres for the acid even though I used a pipette. Every time I washed a test tube or a measuring cylinder, I did not dry it before using it. This may have affected the rate of reaction, as water would dilute the acid. Also, I stopped the stopwatch when I saw the magnesium ribbon disappear, however in reality, the reaction might not have finished, so it leads to inaccurate results. Modification We could have controlled factors in the investigation better such as stirring of the mixed solution because if this is not done properly it can lead to incorrect results. To improve my results, I could dry the test tubes and the measuring cylinder after they are washed to prevent diluted acids. The size and weight of the magnesium would have affected the rate of reaction. The experiment could be improved by measuring, adjusting and weighing the magnesium ribbons so they all are the same size and weight instead of just cutting them to 1.5 cm long. In order to improve the accuracy of my results, I should not use those concentration of acids mixed by hands, because human errors can affect the concentration of the acid. I should also stir the solution to make sure that the concentration of the acid is spread evenly in the test tube to ensure accurate results. ...read more.

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