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The Effect of Concentration on the Rate of a Reaction

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Introduction

Chemistry Investigation The Effect of Concentration on the Rate of a Reaction AIM The aim is to investigate the effect of the concentration of the solution on the rate of reaction. APPARATUS NEEDED 20cm length of magnesium ribbon Emery paper Dilute HCl acid (2M) Distilled water Stopwatch Measuring cylinder Test/Boiling tubes Test tube rack PLANNED METHOD 1. Gather and set up all apparatus. 2. Clean the black magnesium oxide off the strip of magnesium with a piece of emery paper. 3. Measure out 20ml of HCl solution for the first experiment, and pour into a test tube. 4. Drop in the cleaned strip of magnesium ribbon, and start the timer simultaneously. 5. Stop the timer when the magnesium has dissolved completely and there is no more fizzing. 6. Record results into a clearly labeled table. 7. Repeat steps 2-6, but using a lower concentration of solution each time. MEASUREMENTS * Magnesium ribbon = 4cm each time * HCl solution= 1. ...read more.

Middle

CONCLUSION Looking at the results obtained from the two trials of the experiment, I can deduce that the rate of reaction is affected by the concentration of the solution. When there is 20ml of 2M HCl acid with no water, the 2HCL + Mg --> MgCl2 + H2 reaction is completed within around 36 seconds, but with just 5ml of HCl and 15ml of water, the reaction takes much longer, almost 700 seconds (~11minutes). This suggests that a lower concentration means a slower rate of reaction, and a higher concentration means a faster reaction. This is because there are more particles if there is a greater concentration of acid to 'bump' into the magnesium strip, causing it to chemically react and dissolve, and produce hydrogen gas. Adding water to the solution reduces the concentration, and this would explain the fact that more water with the solution gives a slower reaction. EVALUATION AND POSSIBLE SOURCES OF ERROR Although we tried to keep the experiment as accurate and as fair as possible, some of the results were not very consistent. ...read more.

Conclusion

(This would explain the large difference in time for the solution with 15ml acid and 5ml water between the two trials). ? As shown in the temperature experiment, the initial temperatures of all the solutions were different. Temperature is also a factor determining rate of reaction, so this could also explain inconsistent results. WHAT I WOULD DO DIFFERENTLY IF THE EXPERIMENT WAS REPEATED If the experiment had to be done again, I would do the following differently: ??Make the measurements as accurate as possible - make all the lengths of magnesium exactly the same, as well as volumes of acid and water. ??Try and rub off all the magnesium oxide on the magnesium ribbon. ??Try and make the initial temperatures of the solutions the same so that temperature is not a contributing factor of rates of reaction. ??Make sure the thermometer does not get in the way of the reaction so that the results can be as accurate as possible. ??Check and ensure that the reaction is definitely complete before stopping the timer. Heidie Park 11S (N) ...read more.

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