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The purpose of this coursework is to investigate the factors which affect the rate at which zinc reacts with sulphuric acid to form zinc salt and hydrogen.

Extracts from this document...

Introduction

Chemistry coursework Section 1 introduction and aims The purpose of this coursework is to investigate the factors which affect the rate at which zinc reacts with sulphuric acid to form zinc salt and hydrogen. There are a number of factors which affect rates of reaction and for my experiment I investigated the ways in which varying the concentration of sulphuric acid affected the rate of reaction between zinc and the acid. When planning for the experiments, I first tried to understand the theory behind a chemical reaction and the factors affecting rates of reaction. This is explained in Section 2. Based on my understanding of the theory I selected one factor, concentration and made some predictions in Section 3 about how concentration levels affect the rate of reaction. In Section 4, I describe my methods and fair tests together with a list of the apparatus I used. To help in preparing for the investigations I carried out preliminary tests, which are described in Section 5. The results of my investigations are shown in Section 6 and my analyses of these results are found in Section 7. My evaluation is shown in Section 8. Section 2 background information and theory When zinc is mixed with sulphuric acid, a chemical reaction takes place resulting in the production of zinc sulphate and hydrogen gas. The reaction is shown by the equation below: Zn(s) + H2SO4(aq) ZnSO 4 (aq) + H2 Collision theory The rate of reaction can be explained by collision theory. For a reaction to take place two things need to happen, a.) collisions between particles must take place and b.) the collision must have sufficient energy. Molecules are usually moving at different speeds and often bump into each other. Often when they bump they don't react but just bounce off each other because: They aren't moving fast enough for the reaction to take place. ...read more.

Middle

For the first experiment, where I was trying to find out how long it took to produce 50cm3 of hydrogen, I shouted out when 50cm3 of hydrogen had been produced for each concentration of sulphuric acid and my friend recorded the time. In the second experiment, where I was trying to find out the rate of reaction for each 30second time interval. A friend shouted out after each 30seconds had past and I recorded how much hydrogen had been produced. Fig2 Apparatus used. Section 5 Preliminary Experiment Before I carry out the proper investigation, I need to undertake a preliminary experiment in order to highlight any inefficiencies in my methodology so that I could amend them for the real experiment to produce a more accurate set of results. I used the preliminary experiment: 1. To confirm the amount of zinc to use and concentration of sulphuric acid. 2.To establish the induction period, how long it takes for first bubble to appear in order to start timing. 3. To establish how much hydrogen is produced for the first experiment. 4 To establish the most suitable intervals of time or hydrogen, and decide whether to record time taken to produce given amounts of hydrogen or hydrogen produced in given slots of time. From my preliminary experiment I learned that 2grams of zinc and 20cm3 of sulphuric acid was suitable. For my first experiment I chose to use all five concentrations available, whereas for my second experiment I chose to use only 2M and 4M. I also established that 50cm3 was a suitable amount of hydrogen yield, as it wouldn't take too long. For my second experiment I allowed for 100cm3 to be produced. I chose to measure hydrogen yield against allocated time slots of 30seconds. Section 6, Results Obtaining Evidence. The results of my experiments are shown below; Table 1 Reaction times of different concentration level to produce 50 cm3 of Hydrogen Concentration Level Temp �C Time Taken Test 1 Temp �C Time Taken Test 2 Temp �C Time Taken Test 3 Ave Time (mins) ...read more.

Conclusion

I was not able to see a reduction in the rate of reaction as I expected because hydrogen was still being produced when I stopped my experiment and had failed the 100cm3 cylinder I was using, thus I would have needed more time and a bigger cylinder or a smaller amount of the zinc and sulphuric acid. How could I improve the experiments? To achieve better results I could make sure that the surface area of the zinc was the same for each experiment by using a machine to cut out the zinc. I could also ensure that the zinc was free of impurities. I could also make sure that the experiments temperature was kept constant for each test. I could also try to minimise the human error factor of measurements of hydrogen and time by having an alarm clock to beep at specified times, and a dry board marker to mark on the levels of hydrogen produced at each time interval. I could also use a bigger cylinder to ensure that I can carry out the experiment to the end, or alternatively I could reduce the amount of zinc used. What further tests could I do? I could carry out a test that would enable me to measure the rate of reaction until the end when the total amount of hydrogen had been produced. This would allow me to observe the falling rates of reaction as the acid and zinc were being used up. I could also see what impact additional grams of zinc would have on reaction time. I could also see how the other related factors affect the rate of reaction. For example for surface area, I would keep the mass of zinc constant but in different forms up to powder form and see what impact this has on reaction rates. I could also look at temperature and carry out tests to see how a degrees increase impacted the rates of reaction. I could also carry out a test to investigate what impact a catalyst would have on a rate of reaction. ?? ?? ?? ?? 14 ...read more.

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