The rates of reaction Essay Example for Free

The rates of reaction Essay Below are the results of the preliminary testing: Time in seconds As you can see from the results table above the column of 7:3 is not filled up and this is due to timing we did not have enough time in the lesson to complete the full test so we had to leave it, what this informs us is that we either have to reduce the time intervals because of our intervals being 30 seconds it is taking much longer than any body elses, or we have to work at a faster rate. The other reason to why we did not have time to do the last experiment was due to we forgot on several occasions to wash out the conical flask and we often remembered after we added the acid inside and the magnesium, so we had to take it out spill the acid and the magnesium turnings and start all over again because it is not called a fair test if we do not wash the flask out. Other problems that we faced which delayed out time was to put the burette upside down in the water bath, this is because everytime we tried to do this the water contents inside the burette would spill out so we would have to refill the water and try again. From the preliminary testing what I can evaluate is that for some reason there does not seem to be that much difference between the amount of hydrogen produced depending on the amount of concentration . The results seem to be fairly close together and stay in the range of 20 60cm. What I thought would happen is that there would be a drastic change in the results but then if I think about it there would not be a drastic change because we have not used drastic changes in the concentrations so we would not see the clear effects. If I wanted to see big changes in the hydrogen produced then I would have had to have a variety of ranges in the concentration and change is drastically e. g. from 100% to 50%. We ended up doing the experiment with the same concentrations that we used in our preliminary testing this is because we did not mark this problem before, we did not pay attention to the results that much and that was a mistake. I only realised this piece of information when I was analyzing the results and this was too late. The next time when we conducted our proper experiments what happened is that although we used the same magnesium substance magnesium turnings, what was going on was that the rate of the reaction was happening too quickly so in the space of 30 seconds 40cm of water would have been lost, and we were finding that before 210 seconds all the water was finished ,we did not believe it at first so we started up another experiment along side one and it was true the reaction for some reason was really fast and it had defiantly increased in speed since the pilot testing. We then had to change the type of magnesium we were using to magnesium ribbon and we decreased the amount that we were using as well from 0. 2g we decided to use 0. 1 g so that incase the mass of the magnesium was the cause of the fast reaction, by reducing the weight maybe the reaction will slow down. After we changed the magnesium from turnings to powder the reaction between the magnesium and the sulphuric acid was going at the correct speed as before and the reaction happening seemed to look correct. The results tables for the three tests are below: Results 1: Concentrations:100% Above are all the results that we obtained from the three experiments that we conducted. What I am going to do now is collect the mean results and to this what I have to do is add up the cm of hydrogen produced for the concentration of 100% and for 30seconds and divide it by 3 and so on: TIME concentrations. What I can see from this table is that the most amount of hydrogen is produced when the concentration of the sulphuric acid is at its most powerfullest so when the concentration is pure acid. I can tell this because the most amount of hydrogen was produced at the end of the 100% reaction at an average of 73. 3cm. so these results back one part of my prediction and it proved to be correct, but what I can also tell from average results is that as time goes on the amount of hydrogen produced decreased, so this proved my theory of what I thought might happen to be wrong. What I thought would happen is that as time went on the reaction would increase which would mean that the volume of hydrogen produced would be increased, but this was proved wrong because from my average table I can see that at the beginning 90 seconds was when we saw a greater difference between the first volume of hydrogen produced to the next amount in the space of 30 seconds for example from 30 seconds to 60 seconds the volume of hydrogen produced increased from 24.3 to 41. 3 this is an increase of 20cm of hydrogen and from that the volume goes up to 54cm this is an increase of 13. 3cm,but from 90 seconds onwards up to 210 seconds the rate at which the volume increases at is not that sufficient, it increases. By 6,4 then 3.this shows that as time is going on the energy with in the reaction is running out which means that less heat is available for the particles to collide harder and faster to produce the reaction that we are able to see, what is happening as time goes on is that the reaction is loosing he heat energy which is causing the particles to move at a slower speed which means that they are now weaker and that they will not collide more often to produce the hydrogen which in over all basically means that less hydrogen will be produced. After I have produced this table what I have done is that I have plotted these results onto a graph, this graph has all the average results on there so that I am able to compare the results and discus any anomalous results. From the average results graph what I am able to see is that as the levels of sulphuric acid in the solution decreases the amount of hydrogen produced decreases as well. I am distinctively able to see the decrease as the concentration decreases and this is because the lines on the graph decrease at each stage. The average results graph also shows me that during the first 30 60 seconds as the magnesium ribbon comes in contact with the sulphuric acid the levels of hydrogen produced are low, but the thing is that they are low in volume but during the first minute or so is the period of time where I am able to see the greater range between the volumes. So when time does increase the volumes are higher in rate, but not higher between the ranges of each 30seconds. There seems to be more variation during the first minute and a half rather than afterwards. This is visible on the graphs by the steepness of the gradients in the first 30 60 seconds after 90 seconds the gradient starts to curve this is applied to all of the four concentrations. Other general trends that I am able to se by looking at the graph is that as the time approaches to 210 seconds the lines seem to start to curve, this means that if we were to keep recording for a longer period of time the rate at which the hydrogen was being produced would of decreased and the reason to this is that once the energy in the reaction is lost it takes a longer period of time for the particles to come in contact with each other and collide to produce a reaction. I can also see that all four lines end at different volumes of hydrogen. I think that they all end correctly as they do not over take on and other, the reason why I say that they all end correctly is because as the concentration decreases the amount of hydrogen produced should decrease therefore the 100% concentration line should be the line which goes up the highest and the 7:3 concentration line should be the line where the line should end at the lowest amount of hydrogen produced in the whole experiment and this is what has happened therefore the lines are correct in that sense. Evaluation: I think that after we dealt with all the mishaps that we had during the course of the experiments the results obtained were of a good standard and they were reliable results which enabled me to analyse and evaluate them, therefore letting me produce line graphs for the results. I think that the results that I obtained from my experiment are clear and accurate enough, I can say this because when we conducted the experiment for the last three tests we made sure that we followed the safety measurements to ensure that results will be accurate, we did not make any mistakes and remembered to change the water in the measuring cylinder and we also remembered to wash out the conical flask each time we finished with a particular concentration unlike in the preliminary testing . We also made sure that we kept an eye on the time so that we did not exceed the time limit of each experiment and we also made sure that we recorded the results of how much hydrogen was produced as accurately as we could trying to get it to the nearest cm. , because we did all of the above thats why I can say that the results obtained and accurate enough to be used to draw good conclusions and graphs for this investigation. I have found some anomalous results and patterns in the individual experiments not the overall average. If you look at Test 1 graph, then you would see that the lines on the graph seem to over lap each other which is not meant to happen, because in theory what is meant to happen is as the concentration decreases so is the volume of hydrogen produced there for the lines should be in order with the 100% in coming up top followed by the 9:1, 8:2 and the 7:3 results line. But in test 1 results what has happened is that the results for the 9:1 concentration has overlapped with the 100% results. The reason for this is that the results of how much volume of hydrogen was produced for the 9:1 results was higher than the 100% results by 5cm. From the very beginning the 9:1 concentration produced higher results than the 100% concentration at 30 seconds 26cm of hydrogen was produced for the 9:1 testing whilst only 22cm of hydrogen was produced for the 100% concentration, at 150 seconds both sets concentrations had produced the same amount.