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I am measuring the rate of reaction how fast a reaction takes of sodium thiosulphate and hydrochloric acid. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I am going to do two experiments, one changing the temperature and one changing the concentration of the sodium thiosulphate. This is how they will be done. Planning Experimental Procedures Equipment Sodium thiosulphate Na S O of different concentrations Hydrochloric acid HCl Tile marked with a cross Measuring cylinder x2 Beaker x2 Bunsen Tripod Test tube x2 Stopwatch Thermometer As the diagrams show, firstly I will measure the right amount of sodium thiosulphate and hydrochloric acid into two separate test tubes. If it is needed, these will then be put into water and heated with a Bunsen burner and tripod until they are up to temperature, which will be measured with a thermometer in the water. They will then be put into the beaker. Firstly, the experiment will be done with the substances at room temperature. This means that the beaker will be filled with Na S O and HCl via two measuring cylinders and placed on the tile marked with a cross. The amount of Na S O and HCl being put in the beaker will be determined by prior tests, but they will only need to be quite small amounts. As soon as the two substances are mixed together, the stopwatch will start timing and it will stop when the cross is obscured. When the substances need to be heated, they will be put in separate test tubes and heated in a beaker of water as above. They will be mixed together when up to temperature. One of the experiments will show the difference temperature makes and the other will show the difference the concentration of the sodium thiosulphate makes. During the experiments, goggles and aprons will be worn at all times for safety. The tests will be made fair by the fact that only one thing will be changed each time "“ the temperature or concentration of the sodium thiosulphate. We presume that when the concentration of the Na S O is increased, the rate of reaction will be higher. This is because if there are more molecules, they are more likely to collide and react. However, the collision theory says that a very small percentage of these collisions results in a reaction. This is because of an energy barrier. Only those particles with enough energy to overcome the energy barrier will react when they collide. So, if the frequency of collisions is increased, the rate of reaction will increase. However, the percentage of successful collision will remain the same. The particles go through random collisions in which energy is transferred between the colliding particles and this leads to particles with differing energies. The distribution of the energies of a particle of gas is shown by the Maxwell-Boltzmann energy distribution curve, shown below. We would also presume that when the temperature is increased it will have the same effect. This is because the molecules will collide more often and with greater energy and so will be more likely to successfully react because their bonds break. For an average reaction a 10 C temperature rise doubles the rate of reaction because about twice as many particles possess the necessary activation energy. The next diagram shows Maxwell-Boltzmann distribution curves for a fixed mass of gas at two temperatures T and T where T is about 10 C higher than T . The total area under the curve remains the same since there is no change in the number of particles present. So, I predict that in the experiment were the temperature is varied, the rate of reaction will go up as the temperature goes up. In the experiment where the concentration of the thiosulphate is to be varied, I expect the rate of reaction to go up as the concentration goes up. If the concentration doubles, I would expect the rate of reaction to double and if the concentration is zero I would expect the rate of reaction to be zero. In the graph showing temperature compared to rate of reaction, I would expect there to be negative correlation and in the graph showing concentration compared to rate of reaction, I would expect there to be negative correlation. However, it remains to be seen if the results will follow this theory. Here are the results tables that will be used: Temperature 1st results 2nd results Average Rate Of Reaction C seconds seconds seconds seconds Room approx.20 30 40 50 60 70 This is for the first half of the experiment where everything will be kept the same except the temperature which will range from 20 C to 70 C. It is hoped that there will be sufficient time for two experiments and an average will be calculated afterwards. The concentration of the sodium thiosulphate used throughout will be 30g/dm. Concentration 1st results 2nd results Average Rate Of Reaction g/dm seconds seconds seconds seconds 15 20 25 30 35 40 This is the other section to the experiment where everything will be constant apart from the concentration of the sodium thiosulphate. It has been decided that a concentration of no less that 15g/dm will be tested because any less than this would probably take too long. The hydrochloric acid and the sodium thiosulphate will not be heated and the tests will be done at room temperature, usually around 20 C. The experiment will be done twice or three times if possible and the results will be made fair by the fact that only one thing will vary each time. Goggles and aprons will be worn at all times for safety. It has been decided that 5ml of HCl and 20ml of Na S O will be used. Obtaining Evidence These are the results of the experiments: Temperature 1st results 2nd results Average Rate Of Reaction C seconds seconds seconds secs Room approx.20 74.5 69.9 72.2 13.85 30 38.1 38.3 38.2 26.18 40 35.9 39.4 37.65 26.56 50 20.7 18.1 19.4 51.55 60 12.3 9.9 11.1 90.09 70 5.9 5.2 5.55 180.18 Concentration 1st results 2nd results Average Rate Of Reaction g/dm seconds seconds seconds secs 15 125.2 123.5 124.35 8.04 20 74.5 69.9 44.2 13.85 25 53.6 51.2 52.4 19.08 30 49.6 51.6 50.6 19.76 35 45.7 48.8 47.25 21.16 40 22.6 30.5 26.55 44.35 Analysing evidence and drawing conclusions All results have now been obtained and they seem to be quite good, all showing correlation. As was hoped at the start, a repeat was managed for each test and an average worked out from those figures. The results were recorded with decimal place and the averages and rate of reactions are to two decimal places. The rate of reaction is the key thing being looked at in this experiment and this is how it was calculated: 1 Time taken for cross to be obscured This figure was then multiplied by 1000 to make it easier to deal with. The figures have all been rounded to two decimal places. My predictions have been correct. When the concentration of the sodium thiosulphate has gone up, as the first part of the experiment shows, the rate of reaction goes up. When the temperature goes up, as the second results table shows, so does the rate of reaction. This is what was expected and therefore makes it highly unlikely that there have been any major mistakes, although all results are obviously not perfect. The next three pages are graphs. Graphs one and two relate to the first table of results and graph three relates to the second table. The reason there are two graphs for the first table is that one shows time taken for cross to be obscured and the other shows rate of reaction. Rate of reaction is what is being investigated and so only a rate of reaction graph was needed for table two. There are two graphs for the first results table to show the difference in time taken and rate of reaction i.e. the time taken for cross to be obscured shows negative correlation while graph two shows positive correlation. By drawing a line of best fit on the rate of reaction graphs, we can see that there are no results that are obviously completely wrong. With both graphs the last result is suprisingly high, and this can be seen on the results table as well. Evaluating Evidence The procedure used was good and produced good results but it could have been improved and these will be listed later. The results are mainly good, there are no odd results and everything came out as expected. This could mean that the experiment was done perfectly but it doesn't. Although all the average times and rates of reaction all conform to a pattern, they are not all evenly spaced and therefore are probably not perfect. As an example, in the first experiment, where the temperature was being varied, the rates of reaction of 30 C and 40 C were 26.18secs and 26.56secs respectively. This was only an increase of 0.38secs compared to an increase of 90.09secs for 60 C to 70 C from 90.09secs to 180.18secs . Clearly this is an enormous difference and disproportionate. The results could be correct but the results do appear to nearly double each time, except for in this instance. There are similar examples from the second experiment but they are not as obvious. Improvements that could be made if the experiment was repeated: When doing the results that took less time some took around five seconds, it would have been more accurate to have two people so one person could put the substances together while the other person started timing Obviously it would have been good to have done more repeats. Two tests were managed each time but if one had been wrong this could have dramatically changed the average time and therefore rate of reaction. Increasing the surface area of a reactant will increase the rate of a reaction. This is because the reacting particles can only collide with he surface of the solid and the particles within the solid cannot react until those on the surface have reacted and moved away. Powdered calcium carbonate has a much larger surface are than the same mass of marble chips and therefore will react more quickly. All in all I think this was a good experiment and the best that could have been done with the time and resources available. The results supported my predictions and they seem to be fairly reliable results. Aim : We did 4 experiments to find out how the rate of reaction changes with differing concentrations of Sodium Thiosulphate, Hydrochloric Acid and water. As an inert and stable liquid, water was used to alter concentration of Sodium Thiosulphate without changing the end amount of solution. All the atoms in a water molecule have a full outer shell, so they would not react with the other chemicals. WATER IS USED TO SLOW THE REACTION SO THAT IT IS EASIER TO TIME HOW LOG
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I am measuring the rate of reaction how fast a reaction takes of sodium thiosulphate and hydrochloric acid. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I am going to do two experiments, one changing the temperature and one changing the concentration of the sodium thiosulphate. This is how they will be done. Planning Experimental Procedures Equipment Sodium thiosulphate Na S O of different concentrations Hydrochloric acid HCl Tile marked with a cross Measuring cylinder x2 Beaker...
supported my predictions and they seem to be fairly reliable results.

Aim : We did 4 experiments to find out how the rate of reaction changes with differing concentrations of Sodium Thiosulphate, Hydrochloric Acid and water. As an inert and stable liquid, water was used to alter concentration of Sodium Thiosulphate without changing the end amount of solution. All the atoms in a water molecule have a full outer shell, so they would not react with the other chemicals.

WATER IS USED TO SLOW THE REACTION SO THAT IT IS EASIER TO TIME HOW LOG

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Prediction I predict that the...Prediction I predict that the lower the concentration of the hydrochloric acid so there is fewer particles per cm3, the slower the rate of reaction will be. This is because there will be fewer particles in the Hydrochloric acid per cm3, and the solution will be more dilute so less successful collisions will be made due to fewer particles to react with each other. So I think if the Hydrochloric acid is very strong with no water to dilute the substance the cross on the paper will disappear the quickest as I think the most amount of sulpher will be created in the reaction. I think this will happen because there are more of the hydrochloric acids particles per cm3 so the chance of a successful reaction with a hydrochloric particle and a sodium thiosulfate particle is higher so the rate of reaction is faster which causes more sulphur to be given off. But if less reactions take place the rate of reaction will be slower so I think less sulphur will be given off because of this. Here is a Picture showing what I think will happen in a high concentration of sodium thiosulfate and also in a lower concentration. This is called the collision theory. I found these diagrams when I researched about rates of reaction I think reactions will happen faster due to the collision theory. This is where if two particles collide with each other with enough force a reaction takes place. So if there is more of the Hydrochloric acid more reactions take place as the chances of a head on collision which causes a reaction to take place is greater as there is more Hydrochloric acid per cm3 I also think that the reaction will happen in direct proportion. So if the amount of Hydrochloric acid is halved the amount of reactions will also half. I don't have any research to back this up but I think this will happen as it is logical. I also think this will happen because if the amount of Hydrochloric acid is doubled there is going to be double more Hydrochloric acid particles than what was in the solution before so in theory the time it takes for the cross to disappear should be halved and happen double as quick as the time before Here is a prediction graph of what I think is going to happen Method I am going to investigate how different concentrations of Hydrochloric acid and water affect the rate of reaction. As I have chosen to use different concentrations I am going to vary the amount of Hydrochloric acid in the solution. But to keep it a fair test and for the experiment to work I must keep the total volume the same. I am going to have the total volume 40 cm3. To make the experiment a fair test I will always have 20 cm3 of sodium thiosulfate. But I must always have 40 cm3 in the solution so if I have the Hydrochloric acid quite dilute at 10 cm3 I must have 10 cm3 of water to keep the experiment fair to make the total volume all the same. To also keep it a fair test I will also have to keep other variables the same. This is the temperature. To keep this fair I will do the experiment all in one room so there is no difference in temperature and away from windows so the sun can not affect my experiment. This along with always keeping the volume the same will make my experiment a fair test. In my experiment I am going to see how long it takes for different solutions of Hydrochloric acid to produce enough sulphur until a cross on a piece of paper disappears. I will explain how this works now. What I will be doing First of all I will get all of my apparatus which is listed below. I will then set up my experiment. To start this I will put a piece of paper with a thick cross done in pen underneath a beaker. This is what will tell me what the rate of reaction is like. Because if the cross disappears quickly the rate of reaction is high and lots of sulphur is given off because of this as more particles are reacting quicker. But if the rate of reaction is slower it will take longer for the sulphur to cover the cross so it could not be seen. This would mean less reactions were taking place and slower because not as much sulphur is being formed. So that is what I will use the cross for. I am going to keep the level of sodium thiosulfate the same in my experiment and every time at 20 cm3. So in a small measuring cylinder so I can measure the amount more accurately I will use a pippet and measure 20 cm3 into the measuring cylinder. I will then pour this amount into the beaker. After this in a new measuring cylinder so I don't get the two substances contaminated I will measure out the first amount of the hydrochloric acid which I will be using. I will be using the following amounts watercm3 hydrochloric acidcm3 0 20 5 15 All add up to 20cm3 10 10 15 5 17 3* *The last set I had to change as if I had it all water a reaction could not have taken place which was just realized because there would be no particles from hydrochloric acid to react and to cause a reaction. So if I was using 15 cm3 of hydrochloric acid I would measure this amount into a measuring cylinder using a pippet. I would also need 5 cm3 to make the whole solution up to 20 cm3. After adding the 5cm3 of water into the same measuring cylinder I would then add this is to the beaker with the sodium thiosulfate in. Once this is poured in I will use a stopwatch and wait, without stirring or touching the beaker or the solution. I will time how long it takes for the sulpher to fully make the cross on the piece of paper disappear. I will then stop the stopwatch when the cross has disappeared and write down the results in a table. I will then repeat the same procedure with different amounts of hydrochloric acid and water which are shown above. But on each of the different amounts 20cm3 of sodium thiosulfate will always be used. This will make every concentration I try 40cm3. This will help to make it a fair test. I am going to repeat each amount of hydrochloric acid and water 3 times. This will help make my experiment a fair test as I can then take averages and taken 3 results will show any abnormities which I could then repeat ,to try and get a better set of results. In the results table I will have to convert the times into seconds so I can work out averages. Here is a picture of the apparatus set up:- List of equipment Measuring cylinders Pippet Stop watch Beaker Paper cross Hydrochloric acid Sodium thiosulfate Water After finding all of my results for each concentration and making averages I could do a calculation to find the rate of reaction. . This calculation would give me the rate of reaction, which is measured in how many reactions there are per second as the more collisions of particles per second the faster the reaction will be and so the higher the number. To find this out I will first need to take averages from each concentration. After this I would take this number and divide it by 1. This will give me a very small number but will probably come up on my calculator with like 8.8454 with -03 at the top at the end of the number. I would have to change this to standard form. This would be done by moving the decimal place backwards 3 places as it is negative and replacing the digits behind with zeros. So the number would become 0.0088 Here is a example:- say a average is 127 seconds for the cross to disappear. So 1 divided by 127 is 7.8740 -03 so moving the decimal point back 3 spaces the number would become 0.0078. This would be the rate of reaction Water Hydrochloric Acid cm3 Sodium Thiosulphate cm3 Volume cm3 Seconds Time 1 Time 2 Time 3 avr RoR 0 20 20 40 115 113 109 112 0.0089 5 15 20 40 123 125 118 122 0.0082 10 10 20 40 138 135 137 137 0.0073 15 5 20 40 157 161 163-152* 157 0.0064 17 3 20 40 210 218 200 209 0.0048 results * With this result I think I had a abnormity so I decided to retake that result and I came out with 152 seconds which was more like what I had been looking for. I used this result to work out the average. Analysis From my results I have drawn 2 graphs from the results I have collated. In the first graph it shows the rate of reaction and also the concentrations of hydrochloric acid and water. The graph shows that at fully concentrated hydrochloric acid with no water the rate of reaction which happens with the amount of reactions per second that the most happen with 0.0089. At a quite strong concentration of 15 cm3 hydrochloric acid and 5 cm3 water the rate of reaction was also quite high but not as high as the highest concentration. This amount was 0.0082. From this amount it goes down to 0.0073 at a concentration of 10 cm3 acid and 10cm3 water. The next point is then at 0.0064 at 5 cm3 acid and 15 cm3 water. These 4 points go in a very steady line which is quite steep. This shows that the part in my prediction where I said I thought the results would go down in direct proportion is right. But after the 4th point the line on the graph gets even steeper going downwards. I think this is because we made a mistake with what concentrations to use so we used 3cm3 acid and 17 cm3 water so the concentration was a lot weaker than the others. I believe if we had started at 25cm3 hydrochloric acid and nothing of water and then 20cm3 acid and 5cm3 water all of the results would have continued the steady quite steep directly proportional line. ON this graph it also shows that as the concentration decreases of hydrochloric acid the rate of reaction in the solution falls. This is shown from the highest concentration of hydrochloric acid where the rate of reaction of successful collisions in one second was a high value of 0.0089 and at the lowest concentration it was 0.0048 showing the difference in the amount of successful collisions. On the second graph it shows how the change in concentration affects how long it took for the sulphur produced from the experiment to cover the cross so it could no longer be seen. The averages f the concentrations shows a gradual curved line starting at the lowest time for the cross to disappear at the highest concentration which took 113 seconds to the longest time at 210 seconds at the weakest concentration of acid. The graph goes up in a curve from the highest concentration to the weakest concentration. This shows that as the concentration of the hydrochloric acid increases the time it takes for the cross to disappear decreases. I think that it takes less time in higher concentrations for the sulphur to make the cross disappear and the rate of reaction goes up is because of the amounts of particles in the hydrochloric acid. I think that the rate of reaction is higher in the more concentration solutions because there are more hydrochloric acid particles in the solution per cubic centimetre. This means there is a higher chance of those particles colliding with a sodium thiosulphate particle and there being a successful collision because there are more of them. This is backed up with scientific research which I took from a chemistry book "The more concentrated acid has more acid particles per cubic centimetre so these particles will collide with the substance more often causing a reaction to take place if the collision is strong enough" This and my graphs back this up and also what I said in my prediction. I also think more sulphur is produced quicker with higher concentrations because of the collision theory. Because there are more successful reactions per second in higher concentrations due to increased hydrochloric acid particles per cm3 so more sulphur is produced as a waste gas after the reactions take place. So if there are more reactions per second the sulphur is given off more quickly due to this. This is why the sulphur makes the cross disappear more quickly with higher concentrations of acid and why there are more reactions per second with higher concentrations of acid. Here is a equation for the reaction:- HCl + sodium thiosulfate sodium chloride + sulfur dioxide + sulfur + water HClaq + Na2S2O3aq NaClaq + SO2g + Ss + H2Ol This reaction shows the hydrochloric acid and sodium thiosulfate reacting together to produce the other products of sodium chloride + sulfur dioxide + sulfur + water. This is where the sulphur comes from. Evaluation I think my experiment went well and there were good points to it and also bad points. The good points "“ I think I did well to keep all the variables the same except for the concentration, but only on the first day of the experiment. I managed to not let temperature affect the investigation by doing it in the centre of the room to avoid the sunlight. I also kept the beaker absolutely still whilst doing the experiment so I did not affect any other variables. I also think I did well when measuring amounts. For the lower concentrations I used small measuring cylinders so I could be more accurate on how much of the substance was in it. This was also useful when measuring the amount of water. Apart from these good things I feel the experiment could be done a lot better. The first major problem with how I did this experiment was that even though I kept all the other variables the same I took some results on a different day which unsettled my results. The first two results of each concentration were taken on the first day of the experiment and I was getting balanced results with 115 seconds and 113 seconds for the biggest concentration of the acid. But on the third attempt on the same concentration done on another day the time for the cross to disappear was less with 109 seconds. This was the same for all the results I took on the 2nd experiment day. I think the temperature affected the results and it was hotter on the 2nd day to speed up the reaction and act as a catalyst. I could not help this but if I did the experiment again I would try to get it all done on one day so different temperatures on different days could not affect the experiment. If I took all the results on one day it would make the experiment a lot fairer as natural weather effects over different days could not affect my experiment if it was all done on one day. But even with doing the experiment over two days my results kept mostly within 10% with each other. I worked this out by taking the biggest difference over three values of a given concentration and dividing the difference from the biggest and the smallest, so if I had 3 results of 123,127 and 125 the biggest difference is 4. This is then divided by the biggest number which is 127 and multiplied by 100 to turn it into a percentage. So the calculation would be 4/127 multiplied by 100 I don't think I had some within 10% of each other because the experiment was carried out on two different days. I think if the test had been carried out all on one day the results would be a lot more accurate. Another bad thing I thought about the experiment was having to use the naked eye to tell when the cross had fully disappeared. Sometimes I could not tell if the cross had fully disappeared as I could see little glimpses of it. This could affect timings by considerable amounts as I never really new when the cross had fully disappeared. I think this was a major problem with the experiment and how it was carried out. Another thing that added to this problem was that I used two different crosses on the different days, again showing how it should really be carried out on just one day to make it a fair test. If I was to do the experiment again with the same method I would make sure to use just one cross and stick to it. But I think there is another method available if I was to do this experiment again. I could use a realistic computer simulation. On this program it would allow me to change many variables mainly concentration and temperature. Either can be easily adjusted and is very simple to use. I think this would be a very good idea because it would completely be a fair test and no variables other than the one you want can affect it as it is a simulation. On the screen the variable can be changed and on the screen it shows how many reactions there have been. The data given after the experiment has been completed can then be easily put onto graphs and analysed. I think this would be a much better method as it would get rid of the slightly inaccurate method of seeing how long it takes for the sulphur to completely cover the cross. With the simulation it would get rid of all these hassles and I think the results would be a lot more accurate because all the other variables can be kept exactly the same as it is a simulation on the computer. Overall I think the experiment went quite well but the problems with doing the experiment on different days and using different crosses didn't make the experiment that viable or that fair. But even with these problems my results were quite accurate and reliable but I feel could have been made better by preferably using a computer simulation which would be very reliable and accurate   

Prediction I predict that the lower the concentration of the hydrochloric acid so there is fewer particles per cm3, the slower the rate of reaction will be. This is because there will be fewer particles in the Hydrochloric acid per cm3, and the solution will be more dilute so...

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Rate Of Reaction in... Rate Of Reaction in Sodium Thiosulphate and HCl Plan in this experiment I am investigating the rates of reaction, and the effect different changes have on them. The rate of reaction is the rate of loss of a reactant or the rate of formation of a product during a chemical reaction. A rate of reaction is measured by dividing 1 by the time taken for the reaction to take place. There are five factors which affect the rate of a reaction, by the collision theory of reacting particles: temperature, concentration of solution, pressure in gases, surface are of solid reactants, and catalysts. Aim: - my aim is to see the effects of a change in temperature and concentration on the rate of a reaction. The reaction that will be used is: Sodium Thiosulphate + Hydrochloric Acid Na2S2O3 aq + 2HCl aq Sodium Chloride + Water + Sulphur Dioxide + 2NaCl aq + H2O l + SO2 g + Sulphur S s Two experiments will be carried out "“ one changing the temperature while everything else remains constant and one varying the concentration while keeping everything else constant. Both the sodium thiosulphate and the Hydrochloric acid are soluble in water, so the concentration of either can be changed. temperatures and concentrations to use during my preliminary series of experiments "“ 50cm3 of sodium thiosulphate solution and 5cm3 of hydrochloric acid as the experiment one con 1 mol/dm3 of HCl acid concentration will be fixed 10-35g/dm3 of sodium thiosulphate all of these concentrations will be tested in turn going up in steps of 5g/dm3 20-70°C temperature all of these temperatures will be used going up in steps of 10°C Concentrations of 5, and 40 g/dm3 of thiosulphate were available to me but my preliminary work showed that the 5 g/dm3 and 40g/dm3 were too slow and fast respectively in reacting to be worth testing. Similarly any temperature below 20°C reacted too slowly, and 80°C and 90°C reacted too quickly to be worth including in my final results. Using my preliminary experiments I decided on using the following apparatus: 1 thermometer 1 beaker 2 measuring cylinders 1 conical flask 1 tripod 1 gauze 1 heatproof mat 1 stopwatch 1 Bunsen burner X board 1 pair of tongs 1 pair of goggles 1 apron Method: - Experiment 1 - Changing the concentration 5 cm3 of HCl at concentration 1 mol./dm3 and 15 cm3 of sodium thiosulphate at varying concentrations "“ 10 to 35 g/dm3 are poured out into two measuring cylinders and then poured into a conical flask, which is placed on top of a board marked with letter X. The stopwatch will now be started. When the mixture has turned sufficiently cloudy so that the letter X can no longer be seen the stopwatch will be stopped and the time will be recorded. The experiment is repeated with all the concentrations. The whole procedure is then repeated. Experiment 2 "“ Changing the temperature 5 cm of HCl at concentration 1 mol./dm3 and 15 cm of sodium thiosulphate at varying concentrations "“ 10 to 35 g/dm3 are poured out into two measuring cylinders. A beaker is half filled with hot water from a tap. The water is placed on top of a Bunsen on a blue flame and the two measuring placed inside the water bath. The water is heated to the necessary temperature 30°C to 70°C then the two measuring cylinders are taken out and the contents of both are poured into a conical cylinder. The time it takes for the X to disappear is timed and recorded. The experiment is repeated using all the temperatures. The entire procedure is the repeated. Repeat results and averages will be taken to improve the credibility of the findings, and present solid grounding for the final conclusion. The repeat results will help to iron out any anomalies and the average will give a good summary of the results of the experiment. However if one set of results is entirely different to the other, a third experiment will be performed to replace the anomalous set of results. Safety "“ A pair of goggles will be worn during the heating part of the experiment in order to protect the eyes. An apron will also be worn to protect the skin and clothing. When handling hot beakers and measuring cylinders a pair of tongs will be used. A gauze and heatproof mat will be used while heating to avoid any damage to the equipment. Fair Test - In order for my findings to be valid the experiment must be a fair one. I will use the same standard each time for judging when the X has disappeared. I will make sure that the measuring cylinders for the HCl and thiosulphate will not be mixed up. The amount of HCl will be 5 cm3 each time, and the amount of thiosulphate will be fixed at 15 cm3. During the heating stage of the experiment, a blue flame will be used throughout. Also the same Bunsen burner and gas tap will be used to maintain continuity. All of these precautions will make my final results more reliable and keep anomalies at a minimum so thus make the entire investigation more successful. Prediction "“ I predict that as the temperature is increased the rate of reaction will increase. I also predict that as the concentration of the sodium thiosulphate increases the rate of reaction will increase. This means that both graphs drawn up in my analysis will have positive correlation, and will probably be curved as the increase in rate of reaction will not be exactly the same as the concentration temperature is increased. This can be justified by relating to the collision theory. When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully. If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. All this can be understood better with full understanding of the collision theory itself: For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area. Concentration "“ If the concentration of a solution is increased there are more reactant particles per unit volume. This increases the probability of reactant particles colliding with each other. Pressure - If the pressure is increased the particles in the gas are pushed closer. This increases the concentration and thus the rate of reaction. Surface Area "“ If a solid is powdered then there is a greater surface area available for a reaction, compared to the same mass of unpowdered solid. Only particles on the surface of the solid will be able to undergo collisions with the particles in a solution or gas. The particles in a gas undergo random collisions in which energy is transferred between the colliding particles. As a result there will be particles with differing energies. Maxwell-Boltzmann energy distribution curves show the distribution of the energies of the particles in a gas. The main points to note about the curves are: 1. There are no particles with zero energy. 2. The curve does not touch the x-axis at the higher end, because there will always be some particles with very high energies. 3. The area under the curve is equal to the total number of particles in the system. 4. The peak of the curve indicates the most probable energy. The activation energy for a given reaction can be marked on the distribution curve. Only particles with energy equal or greater than the activation energy can react when a collision occurs. Although Maxwell-Boltzmann distribution curves are for the particles in a gas, the same distributions can be used for the particles in a liquid or solid. Effects of a temperature change - The graph below shows Maxwell-Boltzmann distribution graphs for a fixed mass of gas at two temperatures "“ T1 and T2, where T2 is roughly 10°C higher than T1. The total area under the curve remains the same, since there is no change in the number of particles present. A small increase in temperature causes significant changes to the distribution energies. At the higher temperature: 1. The peak is at a higher energy. 2. The peak is lower. 3. The peak is broader. 4. There is a large increase in the number of particles with higher energies. It is the final change that results increase in rate, even with a relatively small increase in temperature. A small increase in temperature greatly increases the number of particles with energy greater than the activation energy. The shaded areas on the energy distribution curves show this. Effect of a catalyst - A catalyst works by providing an alternative reaction pathway that has lower activation energy. A catalyst does not alter the Maxwell-Boltzmann distribution. Because a catalyst provides a reaction route of lower activation energy, however, a greater proportion of particles will have energy greater than the activation energy. Secondary Sources Used: AS Level Chemistry Textbook kinetics module The Internet Dr. Jones's Chemistry Lessons Information sheets from Dr. Jones Obtaining Evidence Temp.°C Time 1 s Time 2 s Average s 20 110.67 107.42 109.045 30 100.13 103.34 101.735 40 64.20 65.92 65.06 50 45.34 37.73 41.535 60 30.12 33.18 31.65 70 18.92 16.34 17.63 Concen.g/dm3 Time 1 s Time 2 s Average s 10 222.63 224.38 223.505 15 150.90 147.03 148.965 20 105.25 105.97 105.61 25 66.04 68.75 67.395 30 55.63 56.1 55.865 35 27.32 25.96 26.64 Temp.°C Rate of Reaction 1s-1 Rate of Reaction 2 s-1 Average s-1 20 0.00904 0.00931 0.00917 30 0.00999 0.00968 0.00983 40 0.01558 0.01517 0.01537 50 0.02206 0.02650 0.02428 60 0.03320 0.03014 0.03167 70 0.05285 0.06120 0.05703 Concen.g/dm3 Rate of Reaction 1s-1 Rate of Reaction 2 s-1 Average s-1 10.00000 0.00449 0.00446 0.00447 15.00000 0.00663 0.00680 0.00671 20.00000 0.00950 0.00944 0.00947 25.00000 0.01514 0.01455 0.01484 30.00000 0.01798 0.01783 0.01790 35.00000 0.03660 0.03852 0.03756 Temp.°C Rate of Reaction 1s x1000 Rate of Reaction 2 s x1000 Average s 20 9.04 9.31 9.17 30 9.99 9.68 9.83 40 15.58 15.17 15.37 50 22.06 26.50 24.28 60 33.20 30.14 31.67 70 52.85 61.20 57.03 Concen.g/dm Rate of Reaction 1s x1000 Rate of Reaction 2 s x1000 Average s 10 4.49 4.46 4.47 15 6.63 6.80 6.71 20 9.50 9.44 9.47 25 15.14 14.55 14.84 30 17.98 17.83 17.90 35 36.60 38.52 37.56 Analysis In this experiment I have found that as the temperature and concentration is increased the time taken for the reaction to take place decreases. This means the rate of reaction increasers as it takes less time for a reaction to take place, so more take place per second. In the temperature experiment the time taken for a reaction to take place decreased by roughly 10 to 15 seconds for every 10°C increase in temperature, with the one anomaly being the 30°C reading. There is also a trend in the increase in rate of reaction as the temperature increases. The difference is always more or less 0.02 s-1, with the same exception. Using the graphs, with lines of best fit, I can draw a conclusion from my experiment. Firstly I can see that with the "time" graphs that plot temperature and concentration against time taken for the reaction to take place the graphs have negative correlation in both cases, meaning that as the temperature concentration increased the time taken for the reaction to take place decreases. The time graph for the temperature experiment has a much steeper curve than the one for the concentration experiment, meaning that the decrease in time taken for the reaction was far more rapid. Naturally, the above means that the both the graphs plotting rate against temperature and concentration have positive correlation "“ as the temperature and concentration are increased so does the rate of reaction. This is because when the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully, and when solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. The graph for concentration shows that when the concentrations were relatively low 10, 15, 20 g/dm3, the increase of rate x1000 was also fairly small increasing from 4.47 to 6.71 to 9.47. There was then a gradual increase in the difference, and between 30 and 35 g/dm3 the rate more than doubled from 17.90 to 37.56s-1. This shows that there are far more collisions at a concentration of 35 g/dm3 than at 30 g/dm3. The graph plotting time against the rate of reaction x1000 shows that the difference of rate between increasing temperatures excluding the anomaly of 30°C was pretty much regular, increasing in steps of 6-10 9.17 to 15.37 to 24.28 to 31.67. However, once again there is a giant gap in the last temperature increase "“ at 60°C the RoR x1000 is 31.67 s-1, and at 70°C it is 57.03 s-1. For this to fully make sense it is necessary to recap the collision theory briefly: For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area.   

Rate Of Reaction in Sodium Thiosulphate and HCl Plan in this experiment I am investigating the rates of reaction, and the effect different changes have on them. The rate of reaction is the rate of loss of a reactant or the rate of formation of...

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Rates of reaction Plan ...Rates of reaction Plan Aim: In this experiment I will find the rate of reaction between Sodium thiosulphate NaS2o3 and Hydrochloric acid HCl. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I will investigate how temperature affects the rate of reaction between Sodium thiosulphate and Hydrochloric acid. Prediction When sodium thiosulphate and hydrochloric acid react they produce a cloudy precipitate. The two chemicals are both clear solutions and will react together to form a yellow precipitate of sulphur, the equation for which is as follows: NaS2O3 aq+ HCll¨Sg+NaCls+ H2Ol+SO2s As the solution will turn cloudy, we can observe the rate of reaction by placing a black cross underneath the beaker and seeing how long it takes for it to disappear. There are factors that affect this experiment such as temperature, concentration and time. I do not think that surface area will affect the experiment, as both chemicals are liquids. For my experiment I will study temperature as this is easily observed and can be easily varied. I think that as the temperature of sodium thiosulphate increases, the amount of time taken for a reaction decreases. I know this because before two particles can react they must meet. The higher the temperature there is the more successful collisions between other particles is increased. When temperature increases the bonds in NaS2O3 break quicker because more energy is available greater than the activation energy of the reaction. As a result S2O3 2- ions are available so it takes less time to bond with H+ ions from HCL and new bonds are formed quicker and therefore sulphur precipitates quicker and the rate of reaction increases. S2o3 2- aq +2H+ aq S02aq+Sg+H2Ol When the temperature increases it causes an increase in kinetic energy so you have more chances of successful collisions between NaS2O3 particles and HCl particles so the rate of reaction increases. Also more activation energy is made available to overcome the activation energy of the reaction; the reactants have greater energy than the activation energy, so the reaction takes place quicker. I will keep the concentration of NaS2O3 constant to prevent more successful collisions as there would be more particles available if a higher concentration is fed which will increase successful collisions. I will also keep the concentration of HCl constant as an increase or decrease in concentration will affect the rate of reaction. I will change the temperature of NaS2O3 so I can see how the temperature affects the rate of reaction. I will keep the temperature of the HCl acid at room temperature as we are only concentrating on the NaS2O3 and if we heat the HCl it might affect the rate of reaction it would not be a fair test if we heat the HCl when we are observing how NaS2O3. I also predict that every time the temperature increases by 10oC the rate of reaction doubles. The preliminary results Time on heat sec Temperature of NaS2O3 0C Time taken for cross to disappear sec 0 24 60 10 34 52 Method For the preliminary experiment I heated the NaS2O3 to get it to the temperature I wanted but it was difficult to get the NaS2O3 to the right temperature so the results were not as accurate, but for my real experiment I will use a water bath to get accurate results instead of a Bunsen burner. For the preliminary experiment I only recorded the temperature of the NaS2O3 but for my real experiment I will record the temperature of the HCl as well to get more accurate results because if the NaS2O3 was high and the HCl could bring the temperature down quicker and also have to make sure all the temperature of the HCl is the same. I will also take the temperature of the mixture so I know the temperature at which the reaction took place. 1. I will set up my apparatus and put an X on a piece of paper and measure out 50ml of NaS2O3 and 10ml of HCl. 2. I will pour the NaS2O3 into a conical flask and measure the temperature and pour the HCl in to the same conical flask and time how long it will take for the cross on the paper to disappear. 3. I will do 4 different temperatures and I will do them three times each to get accurate results. 4. I will record the results in a table of results. Apparatus used Sodium thiosulphate NaS2O3-50ml Hydrochloric acid HCl-1M Conical flaskx2 Measuring cylinderx2 Thermometer Water bath at different temperatures Paper marked with X Stop watch Distilled water Analysis From graph 1 I can see that when temperature increases the time taken for reaction to take place decreased. In graph 2 I can see when temperature increases the rate of reaction increases. There was an anomalous result in graph 2, when the temperature was 480C and 1€time was 1.18. My results agree with my prediction because I predicted that the higher the temperature the lower the time taken for the reaction to take place and we can see this from the graphs. The graph shows this pattern taking place. For my experiment I studied temperature as this is easily observed and can be easily varied. The temperature of sodium thiosulphate increased, and the amount of time taken for a reaction decreased. When temperature increased the bonds in NaS2O3 broke quicker and more energy is available greater than the activation energy of the reaction and S2O3 2- ions are available so it takes less time to bond with H+ ions from HCl and new bonds were formed quicker and therefore sulphur precipitated quicker and the rate of reaction increased. This is why in graph 2, I had a strait line positive correlation graph. When the temperature increased it caused an increase in kinetic energy so we had more successful collisions between NaS2O3 particles and HCl particles and the rate of reaction increased. Also more activation energy was made available to overcome the activation energy of the reaction; the reactants had greater energy than the activation energy, so the reaction took place quicker. I think my results support my prediction because I predicted when temperature increases the rate at which the reaction takes place is faster. In graph 2, the theory that every time the temperature increases by 10oC, the rate of reaction will double did not work in my experiment and the results of that theory is given below: 10"¹C¨0.018 0.024€0.018=1.333 20"¹C¨0.024 0.052€0.024=2.167 30"¹C¨0.052 0.078€0.052=1.500 40"¹C¨0.078 0.086€0.078=1.103 50"¹C¨0.086 0.104€0.086=1.209 60"¹C¨0.104 0.120€0.104=1.154 70"¹C¨0.020 0.1380.120=1.1500 80"¹C¨0.138 Evaluation I think my method worked well as I repeated the experiments three times for five different temperatures and got three results which were similar. I think the experiment worked but when we used NaS2O3 with a high temperature, it was difficult for us to time the reaction as it was more rapid than we had expected. If I had the chance to repeat the experiment I would concentrate on the concentration of the NaS2O3 rather than the temperature as there are a lot of factors which could affect the temperature. I think my experiment was done reasonably well as l got similar results when I repeated them three times. There was one anomalous result in graph 2 and I think there was an anomalous result because the NaS2O3 was at a high temperature and the reactants reacted rapidly that the timing was wrong. I also think this was caused by the open window we worked next to which brought the temperature down quickly. I think my results are fairly reliable and it supports my analysis as I said, when temperature increased the time taken for the reaction to take place decreased. I could try the experiment with different methods and different reactants to get additional knowledge. I could use magnesium instead of Sodium thiosulphate and I could heat the hydrochloric acid instead of heating the NaS2O3 and to make more of a fair test I could make sure all the windows and doors are closed and no cold air comes in.   

Rates of reaction Plan Aim: In this experiment I will find the rate of reaction between Sodium thiosulphate NaS2o3 and Hydrochloric acid HCl. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I will...

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