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# Concentration of Acid Rates of Reaction Investigation

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Introduction

28th February 02 Year 10 Science Coursework Rates of Reactions Introduction This year in chemistry we have been studying different types of reactions and what affects their rate. To help with this work, we have been given an experiment to investigate and analyse the factors influencing the rate. What is the rate of a reaction? The rate of a reaction is a measurement of its speed. It is calculated by measuring how quickly reactants are used up or products are formed. (Usborne Illustrated Dictionary of Science) Planning Our task is to investigate ONE of the factors affecting a particular reaction. The reaction we are going to investigate is:- Magnesium + Hydrochloric acid --> Magnesium Chloride + Hydrogen Mg + 2HCl --> MgCl2 + H2 I have chosen to investigate this reaction because it will be easy to measure the rate. Hydrogen gas is given off and so I will be able to collect and measure it. Many factors can affect the rate of a reaction. * Temperature * Surface area of magnesium * Use of a catalyst * Concentration of acid The Collision Theory For a reaction to take place between two substances, their particles must collide, so if more collisions occur, the rate of the reaction increases. However only some collisions are successful. This is because not all particles have enough energy to break bonds in other particles. We can alter the conditions under which the reaction takes place so that more collisions occur in a given period of time and so that the rate will increase. Temperature When the reactants are heated, the rate generally increases. When the reactants are cooled, the reaction generally goes slower. According to the collision theory, particles must collide in order to react. ...read more.

Middle

The lowest concentration is 0.25M. To get this I will use 10cm3 of 1M acid and 30cm3 of water. The highest concentration is 2M. To get this I will use 40cm3 of 2M acid. Measuring out acid and water by hand is quite accurate but there is the possibility that I could measure it out wrong. During my preliminary work, I tried the 0.25M experiment several times and found that the experiment stopped before enough gas was produced, and also the rate was too slow, so I decided not to do this concentration in my main experiment. I also had a few problems with dropping in the magnesium, putting in the bung and starting the stopwatch all at the same time, so I had to get a friend to help. A lot of the time, I was not getting enough gas, this was probably because I was not putting the bung in quick enough so some gas was escaping. At first I tried taking a reading every 10secs, but for the lower concentrations there was hardly any change and in the higher concentrations, it was going too fast to take that many readings, so I decided to take a reading every 20secs instead. Preliminary work results Concentration Experiment 1 Experiment 2 Experiment 3 0.25M Didn't finish Didn't finish Didn't finish 2M 10.9 secs 11.5 secs 10.5 secs I didn't try 0.5M in my preliminary work, as the 0.25M reaction was never that far off finishing, so I knew that there wouldn't be any problems with the 0.5M. So now the range of concentrations I am going to use are:- 0.5M 0.75M 1M 1.5M 2M Prediction * The higher the concentration of acid, the faster the reaction will go. ...read more.

Conclusion

The higher the concentration, the faster the reaction will go. Evaluation My experiment is not 100% reliable, although it is quite accurate. There are things which could have altered my results so that they are not as accurate as they could have been. However these errors would only be small. * On some occasions I was rushing in the lesson and I may have not measured everything correctly. For example, if I had made the acid too concentrated then the rate would have gone faster, as there would have been more acid particles to collide with the magnesium particles. * At the start of each experiment, I had to drop the magnesium into the flask, put in the bung and start the stopwatch all at the same time. Even though I got a friend to start the stopwatch for me, sometimes I didn't put the bung in quick enough, and some gas may have escaped. As all the points on my graph lie more or less on the curve, I can say that there are no anomalous results. I think my results are reliable because I did each experiment 3 times. These repeats accounted for any anomalous results. Further work If I wanted to add proof to my results, or find other trends and patterns I could carry out some further work. This could include: - * Try the same reaction again but with a different acid or metal to see if I get the same patterns. * Investigate a different reaction to find other patterns in the rate. To improve the experiment I have done, I could keep a constant temperature for my reaction by using a water bath. This would ensure that temperature is not a factor affecting the rate. This document was downloaded from Coursework.Info - The UK's Coursework Database ...read more.

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Time (secs) 0.8M 0.9M 1.0M 1.1M 1.2M 0 0 0 0 0 0 5 2.7 2.7 4.5 5.7 6.7 10 5 5 9 11.3 13.3 15 7.3 8.3 13.5 17.3 19.3 20 9.7 10.7 18 22.7 24.3 25 13.3 13 21.5 26.7 28.3 30 16 15 25 29.7 32 35