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Rates of reaction.

Extracts from this document...

Introduction

Rates of reaction In Chemistry we were doing a topic on rates of reaction. I have found out that a reaction rate can be changed by changing concentration, Temperature, surface area and adding catalyst. In this reaction I am going to investigate the changing of the concentration. I have seen in other experiment increasing the concentration one of the chemical makes the reaction go faster. By doing this the rate will increase. In this reaction sulphur is formed and it is a yellow solid and makes the solution go cloudy. In my coursework I am going to investigate the reaction between hydrochloric acid and calcium carbonate. The word equation for this reaction is: Hydrochloric + Calcium Calcium + Water Acid Carbonate Chloride +Carbon Dioxide The symbol equation is: 2HCL (aq) + CaCO3 CaCL2 (aq) H20 ( l ) + CO2 (g) Key Variables All the substances are made up of some particles. The particles could be atoms, molecules or ions. Before we can get a reaction particles must collide with each other and create a reaction. This is the collision theory. The factors that affect the rate of this reaction are temperature, concentration, surface area, and catalysts. Temperature is a factor that affects the rate of reaction because it causes more collisions because the heat is giving the particles more energy. This must happen because reactants most collide with sufficient energy to break old bond and form new ones. ...read more.

Middle

I can see from my preliminary work that it is quite hard to start a stopwatch, pour acid and stick a bung into a boiling tube all at the same time, so I will get someone to assist me while doing so. Investigation results I have carried out the real investigation now and I have used the same method as my preliminary work. I will try to keep this is a fair test and try to realise the rates of reaction. I am going to do three experiments. Fair Test In this test I am going to make it fair by making sure all the equipment is the same and that the only variable is the concentration of the acid. I will need to keep the calcium carbonate at the same weight each time to keep the test fair. Also make sure that the acid has the same amount each time or the test will be biased. Results Here are my results for the three experiments I have done. Expt 1 Concentration of acid (cm2) Time(s) 0.25 0.5 1 1.5 2 20 3 4 6 9 15 40 4 5 20 35 50 60 6 7 30 52 72 80 7 9 40 67 94 100 8 11 48 83 120 9 14 55 95 140 10 17 64 Expt 2 Concentration of acid (cm2) Time(s) 0.25 0.5 1 1.5 2 20 1 2 5 21 17 40 3 5 10 41 48 60 8 12 32 59 70 80 10 20 40 78 94 100 12 22 48 92 120 15 23 55 140 17 27 64 Expt 3 Concentration of acid (cm2) ...read more.

Conclusion

This is likely to be because of the relatively small amount () of CO2 collected (see evaluation) which did not allow each reactant to be used up and all possible collisions completed. Evaluating evidence I think the results I collected are sufficient to support a firm conclusion but the reliability of a small amount of the data was in doubt. At 2.0 of concentration and at 100 seconds, Experiments 1-3 had to be ignored in the final averages as an anomalous result. This could be due to experimental error. It may have been that the temperature was slightly higher than 100 cm2 giving a faster result. It may have been that because the results were cumulative, the stopwatch was started too soon for each results being inaccurate. To improve the accuracy of the experiment, instead of leaving the acid for 10 seconds, I would measure the temperature of the acid and start the experiment when it gets to the correct temperature. This will make the experiment more accurate as I will know the acid has changed to the correct temperature.0 I could also have used a more accurate measure of marble chip by weighing each one. If more time had been available, I would have allowed each reaction to be completed i.e. waited until all of the carbon dioxide had been given off, so that I could see if the reaction rate for each temperature got slower over time. In order to do this, I would need to change the apparatus i.e. use a larger syringe to collect the gas as the size of the original syringe (100cm2) was a limiting factor ...read more.

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