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GCSE CHEMISTRY COURSEWORK: Titrations
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Titrations Introduction: In this experiment we are going to be testing to see which antacid tablet works the best in helping us get rid of stomache aches. From our preliminary experiment, the results we got told us that Rennie was the best antacid tablet with the most accurate results and was also the best tablet in strength. Neautralisation basically occurs when the right amounts of acid and alkaki react. Aim: The aim of this experiment is to find out which antacid tablet works the best in removing stomache aches the quickest. Key Factors: In...
weights and by taking 1g pf each tablet our results would be fair.

To make our method more accurate we could test each tablet on people who have stomache aches and see which one is more effective. We could also test the pH of a stomache and see which tablet would be most suitable.

Another improvement to our experiment would be to get slices of the stomache and let it grow to see what happens and then test the tablets. We could also do the test more times and see if we get the same results.

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The following shows the collision theory...The following shows the collision theory used to explain the effect of temperature and concentration Prediction: In this investigation I expect to find as I increase the temperature the reaction will take place faster. This is because as the temperature increases, it gives more energy to the sodium thiosulphate and hydrochloric acid particles causing them to collide more often and with more force; this increases the rate of reaction. As the temperature rises, a greater number of sodium thiosulphate and hydrochloric acid particles have energy greater than the activation energy therefore leading to more successful collision, and increasing the rate of reaction. * Plan: I will be mixing the two clear liquids 'Hydrochloric Acid' 1M "“HCl and 'Sodium Thiosulphate Solution' 40G/L - Na2S2O3, in order to observe and analyse the reaction changes if any when I increase the temperature. I will add 50cm of weak sodium thiosulphate and 5cm of hydrochloric acid into the beaker; I will make a quick mix of the solution before beginning to start the clock. I will watch the reaction and try to find out whether the solution goes milky and the cross disappears, this will indicate whether the reaction is done. Once the cross has disappeared in the solution I will stop the clock and record the results. Place Apparatus in middle of desk: Boiling tube, test tube, 600ml beaker, kettle, Distilled water bottle, Sodium Thiosulphate, Hydrochloric Acid, Stop Clock, Paper Cross, 25ml measuring cylinder, 100ml measuring cylinder and 10ml measuring cylinder. I will then draw a cross of any size on a piece of A4 paper Prepare Batch of sodium thiosulphate and distilled water using both a 100ml and 25ml measuring cylinders. Place 10cm of Hydrochloric acid into test tube using 10ml-measuring cylinder. Place 50cm of sodium thiosulphate/distilled water solution into boiling tube using a 25ml-measuring cylinder. Put water in kettle and switch on Place a cross on the outside of the 600ml beaker Place 150ml of cold water into 600ml beaker Mix the hot and cold water in beaker Use Thermometer to take the temperature of the sodium thiosulphate and distilled water and Hydrochloric acid with two thermometers in each test tube Wait for the temperature of both the Solution and Hydrochloric Acid to reach the required temperature Pour Hydrochloric acid into solution and start stop clock immediately Wait until cross disappears because of the cloudy solution, and then stop the stop clock Record the time in table Take the temperature of the mixture and record in table Pour away as soon as possible Wash boiling tube out with cold tap water then rinse with distilled water Take average of the start and finishing temperatures and times Repeat Experiments twice for each temperature to improve reliability or to make them reliable. Plot on graph The temperatures that I will carry out the experiments at 25, 30, 35, 40, 45°c. Fair test: I will be able to make this a fair test by keeping all of the solution the same amounts 50cm of weak sodium thiosulphate and 5cm of dilute hydrochloric acid. I will keep these variables the same: Concentration of 2HCl: Concentration of sodium thiosulphate and Hydrochloric acid "“ The concentration of sodium thiosulphate and hydrochloric acid will be kept the same, as to make it a fair test, because if you change the concentration of one reactant it changes the number of particles making the reaction unfair and not reliable. If you create batches of the reactants you reduce the percentage error of volume measurement and of the concentration. E.g. when you measure 25ml of water from a 25ml measuring cylinder a certain amount of water will stay in the cylinder, Then instead of water it was hydrochloric acid and some was left behind, it would change the total concentration because the number of particles has been reduced therefore there is less particles for the other reactant to collide with, also the chance of the amount left behind being the same will be small Volume of Na2S2O3: If I don't keep this constant then it'll effect the reation. Volume of 2HCl: if I don't keep this constant then it'll effect the reation. Temeperature of solution: If I don't keep this constant then it'll increase the energy of the particlesand also increase the chance of a successful collision. I will use the same cross for the whole experiment, also time it accurately and make sure my equipment is working. Equipment: Diagram *Sodium thiosulphate Hydrochloric acid Distilled water 2 Beakers Cross of A4 paper Burette Stopwatch Goggles Funnel Thermometer Water bath To follow this reaction you can measure how long it takes for a certain amount of sulphur to form. You do this by observing the reaction down through a conical flask, viewing a black cross on white paper see diagram below. The X is eventually obscured by the sulphur precipitate and the time noted. By using the same flask and paper X you can obtain a relative measure of the speed of the reaction in forming the same amount of sulphur. Mixè *èOngoing*èWatch stopped* Here is the preliminary result: * Safety: I will make the experiment safe by wearing goggles while handling the irritants and when the reactions are occurring during the experiment. Sulphur and sulphur dioxide are given off during the reactions and are irritants, if breathed in it is dangerous. To avoid this occurring I will keep the room well ventilated by opening windows so the gas can disappear. Each try I do I wash out the beaker several times before starting the experiment. I will make sure the hydrochloric acid does not get in contact with my hands. Analysis: The experiment shows, that when the hydrochloric acid is added to the sodium thiosulphate, a cloudy precipitate appeared. It also shows that when you increase the temperature at which a reaction is taking place, the particles move more quickly resulting in a faster reaction. This has two effects: 1 More collisions take place 2 When a collision occurs, there is more chance that the collision will lead to a reaction, because the amount of energy is more likely to be greater than the minimum amount of energy needed the activation energy Raising the temperature makes the particles move faster. This means that the particles collide more frequently with each other and the rate of the reaction increases. Also, the faster the particles are travelling, the greater is the proportion of them which will have the required activation energy for the reaction to occur. Refer back to prediction diagram HCl+sodium thiosulphatesodium chloride+sulphur dioxide+sulphur+water. HClaq + Na2S2O3aq NaClaq + SO2g + Ss + H2Ol Evaluation: I believe that my results, in general, were very much accurate as I repeated my experiment twice to be able to get an average time taken for the reaction to take place. Providentially, I had no anomalous results which proved the precision and accuracy of my experiment. The method did show the relationship between the temperature and the rate of the reaction. The line graph proves my hypothesis to be correct, but also provides me with some additional information. I have marked on the exact points of the average rate of reaction for every 5 ºC, you can see that at temp 30ºC the speed of reaction did not fall on the line of best fit. This was because the temperature was increased from the previous temp of 25ºC. At 25ºC, the particles would be moving quickly, but not as quickly as they are 30ºC, because as the temperature is increased the particles started moving more quickly and more frequently colliding with more energy so that a faster reaction occurred. Drawing in a line of best fit onto my graph, made it easier to get a more accurate picture from the results. My line graph showed positive correlation meaning that as the temperature was increased the rate of reaction increases. It's also a curve, levelling off gradually. For my Experiment, by having a 5°c rise in temperature allows the number of particles that have energy greater than the Ea Activation Energy 5.45times larger than the number before. This tells me that for this reaction the rate of reaction is almost double for a 5°c rise, therefore shows that the variables were controlled to a sufficient degree of accuracy to allow the reaction to take place at an optimum rate. The experiment was fair and reliable. However, to collect results that are far more accurate, I could have used a mechanical stirrer to act as a catalyst for speeding up the rate of reaction. This would become more precise and dependable. Another factor that we could have improved is the repetitions of experiments; I could have completed the test a further one more time to give me a more adequate average of my results. It was difficult to be able to get both the substances to the required temperature at the same time due to many human errors that can occur. Overall, from my investigation, I believe that the data provides sufficient evidence to support my collision theory as when I increased the temperature the rate of reaction increased. This has turned out to be a successful experiment.   

The following shows the collision theory used to explain the effect of temperature and concentration Prediction: In this investigation I expect to find as I increase the temperature the reaction will take place faster. This is because as the temperature increases, it gives more energy to the sodium thiosulphate and...

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I will be investigating how... I will be investigating how the concentration of hydrochloric acid affects the rate of reaction between hydrochloric acid and magnesium ribbon. Equation: Mgs+2HClaq→MgCl2aq+H2g Planning: The input variables are: "¢ temperature of acid "¢ concentration of acid "¢ surface area of magnesium "¢ use of catalyst I will measure the concentration of acid and control the temperature of acid, surface area of magnesium, mass of magnesium and use of catalyst. The temperature of the acid will effect the rate of reaction because as the acid particles heat up, they gain kinetic energy, therefore move faster and collide more often and more successfully because the collisions are more energetic, therefore there are more collisions in a given time, and the rate of reaction increases. The surface area of the magnesium will effect the rate of reaction because the larger the surface area, the more collisions can take place in a given time, and the rate of reaction increases. The use of a catalyst will effect the rate of reaction because they give an alternative pathway that has a lower activation energy, therefore more of the collisions will result will result in reaction because they need less energy to be successful. This is the apparatus I will use: I will place some magnesium in a flask with an amount of acid. I will place a bung on the tube to prevent any gas from escaping. A tube will run from the flask to a graduating tube in a trough, both filled with water. I will then measure the amount of gas given off in a certain time. I will repeat the experiment 3 times in order to highlight any anomalies. In order to work safely, I will wear goggles in order to protect my eyes from acid. Prediction: I predict that the higher the concentration of the acid, the faster the rate of reaction. This is because there will be more acid particles in a given volume, therefore there are more collisions in a given time, and the rate of reaction increases. If the concentration was to double, I would expect the rate to double. This is in reference to a previous experiment with a reaction between marble chips and various concentrations of acid. It was proved in this experiment that doubling the concentration of the acid doubled the rate of the reaction, therefore the two sets of results were directly proportional. Pre-test: The concentrations we decided to use as our upper and lower values were 2M and 0.2M. From our pre-test, we discovered that 0.2M took too long to react, so the concentrations that we chose were not workable. We then decided to change our lowest concentration to 0.6M. Concentration of Acid M Time to react seconds 2 8.81 0.6 65.90 From the results of my pre-test, I will use 3cm of magnesium and measure the time to collect 10cm3 gas, as these provided workable results. Obtaining Evidence: Concentration of Acid M 1 2 3 2.0 8.52 7.84 8.42 1.8 11.52 6.49 9.12 1.6 9.35 16.02 10.01 1.4 13.95 11.58 11.21 1.2 13.25 13.78 16.05 1.0 18.81 18.24 20.72 0.8 32.78 32.81 22.02 0.6 67.51 48.28 62.46 Concentration of Acid M Temp Before ˚C Temp after ˚C Temp Before ˚C Temp after ˚C Temp Before ˚C Temp after ˚C 2 23 29 20 20 23 30 1.8 23 29 22 22 23 30 1.6 23 29 22 22 24 28 1.4 23 30 21 21 23 27 1.2 23 31 23 23 24 27 1 23 27 23 23 24 27 0.8 23 25 23 23 24 26 0.6 21 23 22 22 23 25 Concentration of Acid M Average Time seconds Rate x100 2 8.260 12.107 1.8 10.185 9.818 1.6 10.010 9.990 1.4 12.246 8.166 1.2 14.915 6.705 1.0 19.256 5.193 0.8 29.203 3.424 0.6 64.985 1.539 Results in bold are anomalies. Analysing and Conclusions From the temperatures taken before and after the reaction, I have discovered that the reaction is exothermic. My graphs show that the higher the concentration of acid, the faster the rate of reaction. This is because there are more acid particles in a given volume, therefore more collisions in a given time, therefore increasing the rate of reaction. If the concentration was doubled, there would be double the amount of acid particles in a given volume, double the amount of successful collisions in a given time, therefore the rate of reaction should double. This means that the concentration of acid and rate of reaction are directly proportional, as stated in my prediction. However, form looking at my results table, I have discovered that the rate of reaction is the concentration of the acid squared. This disagrees with my original prediction. Evaluating: The readings on my graph do not fit the best-fit line very well, as there are several anomalies, therefore the results are not very reliable. The anomalies could be due to the fact that we had to use two different bottles of acid during the experiment, so the concentrations could have been slightly different. We did parts of our experiment at different times, so the temperature in the lab could have been higher, therefore increasing the temperature of the acid, so the particles would have more energy, move faster, increasing the number of collisions, therefore altering the rate of reaction. Where the magnesium had oxidised, a substance had formed on the surface on the magnesium, which meant that the acid had to get through it to reach the magnesium, increasing the time to react. We did however try to make our data more accurate by using a syringe to measure small amounts of acid and water, and using as many decimal places as we could in our calculations. The temperature of the acid was hard to control, as it was controlled by the temperature of the room. If I was to repeat the experiment, I would use more varied concentrations in order to show more clearly the pattern, and also to attempt to clear any anomalies. I would also like to investigate larger concentrations of acid, but would have been hard to measure.   

I will be investigating how the concentration of hydrochloric acid affects the rate of reaction between hydrochloric acid and magnesium ribbon. Equation: Mgs+2HClaq→MgCl2aq+H2g Planning: The input variables are: • temperature of acid • concentration of acid • surface area of magnesium ...

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For this investigation I am... For this investigation I am reacting magnesium ribbon Mg with Hydrochloric acid HCl I am measuring the rate of reaction between the two, and to do this am measuring the hydrogen given off by the reaction. Magnesium is a shiny silver coloured metal, an element with an atomic number of 12, which belongs to the group 2 alkali metal group; it therefore has only two orbiting electrons and is very unstable and reactive. Hydrochloric acid is a solution of hydrogen and chloride a colourless acidic gas in water, Hydrochloric Acid has a high acidity and therefore will react with an alkali metal, the magnesium will displace the hydrogen and bond with the chlorine giving off hydrogen gas and producing the salt magnesium chloride. To keep the experiment fair I must look at all the factors in the reaction, firstly the concentration of the hydrochloric acid is important because it determines how fast the reaction will happen, more HCl molecules in the hydrochloric acid solution will produce more collisions with the magnesium and dissolve it quicker this is the only variable which I am planning to vary, I will keep the different variations of acid in different containers to prevent contamination and will wash out containers before I use them too, the heat of the reaction will also determine how fast it takes place, more heat means more movement of molecules and more collisions between the HCl and the Mg particles, the amount of magnesium will also effect the reaction rate so I will use measured amounts that are all the same, and the surface area of the magnesium must be kept constant too because more surface area means more collisions and effects reaction speed, the apparatus used will be kept the same to give the reaction the same amount of room to take place in, keeping the equipment still which will reduce vibrations which in turn effect the reaction rate, the amount of hydrochloric acid used will be kept constant too because more HCl acid means more HCl molecules to collide with the magnesium, there is also the pressure at which the reaction takes place which will cause more reaction because the particles would be pushed closer together, although the gas given off would have to be measured at room pressure or the volume would be changed by the pressure, The issue of room temperature and the starting temperature of the solution will also be kept constant by keeping the acid bottles in a constant temperature and measuring the temperature at the beginning of the experiment to make sure that this temperature stays the same and therefore there will be a constant amount of activation energy and the reactions will start with the same amount of heat present and therefore will start at the same rate of reaction if no variables were changed. I am not planning to vary the pressure because it brings up to many complications and is not needed, I will start the stop watch as soon as the magnesium ribbon hits the acid and close the bung instantly, also to do this someone else will time for me while I handle the magnesium and close the bung up, I will also clean the jar in which the reaction was carried out to prevent inconsistencies in the strength of acid and possible side effects caused by residues left from the reaction. To carry out the experiment we will be using a conical flask which the reaction will take place in, a bung with tubes coming out of it for the gas to flow down, 4 small measuring cylinders to measure the amount of acid used the measuring cylinders measure in ml, which is equivalent to cm3 in a ration of 1:1 so we can use them to measure the volume of the gas, a margarine tub filled with water and a large measuring cylinder filled with water which will be put upside down in the water to measure gas produced by the reaction, varied strengths of hydrochloric Acid in 10ml quantities, Magnesium ribbon in4cm lengths, a stop watch to time the reaction, and safety goggles for protection from acid splashes. The hydrochloric acid will be put in the conical flask, the magnesium will be dropped in to start the reaction, the bung will be promptly placed on top of the conical flask, from the bung tubes run in to the margarine tub full of water and under the measuring tube so that when the reaction takes place gas will be pushed through the tube and collect in the measuring cylinder. There will be 4 variations of the acid strength, 2 molar, 1.5 molar, 1 molar, and 0.5 molar. I predict that the higher the concentration of the acid the quicker the reaction, but there will be a point where all the magnesium is depleted and the reaction rate will level out, some of the weaker concentrations will not reach that level, but some of the stronger ones should and there will be a point where there is no more magnesium to react and the gas is no longer produced. Before I did the actual experiments I tried some preliminary tests with some 1m acid and some 2m acid, the hydrogen was produced as soon as I dropped the magnesium ribbon in the acid, and the 2m acid reaction finished quicker than the 1m acid reaction, this determines that my original assumption was correct and the magnesium was dissolved quicker in the 2m acid, although both reactions produced the same amount of gas because I used the same amount of magnesium and therefore the reaction was limited to the amount of magnesium to react with, I tested the gas produced under a flame and it produced a high pitched squeak which indicated the presence of hydrogen and proves more of my hypothesis correct and I can determine that when the magnesium ribbon reacts with the hydrochloric acid, magnesium chloride is formed. Here is a graph to show my preliminary test results. Time 1m HCl 2m HCl 30 "“ 0:30 22 cm3 43 cm3 60 "“ 1:00 33 cm3 45 cm3 90 "“ 1:30 43 cm3 46 cm3 120 "“ 2:00 45 cm3 46 cm3 150 "“ 2:30 46 cm3 46 cm3 180 "“ 3:00 46 cm3 46 cm3 210 "“ 3:30 46 cm3 46 cm3 240 "“ 4:00 46 cm3 46 cm3 It would appear that the reaction levels out at the point where 46 cm3 of hydrogen gas is produced when using a 4cm long piece of magnesium. I wrote down the equation to show the reaction between the 2 reactents: Magnesium + Hydrochloric acid = Magnesium Chloride + Hydrogen Mgs + 2HClaq = MgClaq + Hg I will repeat each experiment 4 times to smooth out inconsistencies and be able to produce an average result. To ensure that the experiment is carried out safely I will wear protective goggles at all times when handling acid, stand up while doing experiments to get out of the way quickly in the case of acid spills, and keep a clear and tidy workspace around me to prevent things getting in the way and being damaged by acid. With the equipment set up I would drop the magnesium In to the acid, then begin timing for a set amount of time even if the reaction had finished, and measure the gas produced in the large measuring cylinder and note the volume every 30 seconds for 4 minutes. Here are my 4 results tables Time 0.5m HCl 1m HCl 1.5m HCl 2m HCl 30 "“ 0:30 7 cm3 23 cm3 39 cm3 43 cm3 60 "“ 1:00 12 cm3 34 cm3 42 cm3 45 cm3 90 "“ 1:30 19 cm3 42 cm3 45 cm3 47 cm3 120 "“ 2:00 26 cm3 46 cm3 47 cm3 47 cm3 150 "“ 2:30 30 cm3 46 cm3 47 cm3 47 cm3 180 "“ 3:00 34 cm3 46 cm3 47 cm3 47 cm3 210 "“ 3:30 37 cm3 46 cm3 47 cm3 47 cm3 240 "“ 4:00 39 cm3 46 cm3 47 cm3 47 cm3 Time 0.5m HCl 1m HCl 1.5m HCl 2m HCl 30 "“ 0:30 7 cm3 21 cm3 38 cm3 44 cm3 60 "“ 1:00 11 cm3 35 cm3 43 cm3 46 cm3 90 "“ 1:30 16 cm3 42 cm3 45 cm3 47 cm3 120 "“ 2:00 27 cm3 47 cm3 48 cm3 47 cm3 150 "“ 2:30 32 cm3 48 cm3 48 cm3 47 cm3 180 "“ 3:00 35 cm3 48 cm3 49 cm3 47 cm3 210 "“ 3:30 37 cm3 48 cm3 49 cm3 47 cm3 240 "“ 4:00 40 cm3 48 cm3 49 cm3 47 cm3 Time 0.5m HCl 1m HCl 1.5m HCl 2m HCl 30 "“ 0:30 6 cm3 20 cm3 38 cm3 44 cm3 60 "“ 1:00 12 cm3 33 cm3 43 cm3 47 cm3 90 "“ 1:30 17 cm3 43 cm3 46 cm3 48 cm3 120 "“ 2:00 26 cm3 48 cm3 49 cm3 48 cm3 150 "“ 2:30 29 cm3 49 cm3 49 cm3 48 cm3 180 "“ 3:00 34 cm3 49 cm3 49 cm3 48 cm3 210 "“ 3:30 36 cm3 49 cm3 49 cm3 48 cm3 240 "“ 4:00 39 cm3 49 cm3 49 cm3 48 cm3 Time 0.5m HCl 1m HCl 1.5m HCl 2m HCl 30 "“ 0:30 8 cm3 25 cm3 40 cm3 45 cm3 60 "“ 1:00 13 cm3 35 cm3 47 cm3 47 cm3 90 "“ 1:30 19 cm3 42 cm3 49 cm3 49 cm3 120 "“ 2:00 26 cm3 49 cm3 49 cm3 49 cm3 150 "“ 2:30 32 cm3 50 cm3 49 cm3 49 cm3 180 "“ 3:00 36 cm3 50 cm3 49 cm3 49 cm3 210 "“ 3:30 39 cm3 50 cm3 49 cm3 49 cm3 240 "“ 4:00 42 cm3 50 cm3 49 cm3 49 cm3 These are the 4 sets of results, I recoded 2 each lesson, the last results seem to be react slightly quicker than the others, this could be due to temperature of the room or contamination of the equipment, the reactions seem to have happened quicker, although they don't seem to be too random and I will use them in my average table set of results. Time 0.5mHCl 1mHCl 1.5mHCl 2mHCl 30 "“ 0:30 7 cm3 22.25 cm3 38.75 cm3 44 cm3 60 "“ 1:00 12 cm3 34.25 cm3 43.75 cm3 46.25 cm3 90 "“ 1:30 17.75 cm3 42.25 cm3 46.5 cm3 47.25 cm3 120 "“ 2:00 26.25 cm3 47.5 cm3 48.25 cm3 47.25 cm3 150 "“ 2:30 30.75 cm3 49 cm3 48.25 cm3 47.25 cm3 180 "“ 3:00 34.75 cm3 49 cm3 48.5 cm3 47.25 cm3 210 "“ 3:30 37.25 cm3 49 cm3 48.5 cm3 47.25 cm3 240 "“ 4:00 40 cm3 49 cm3 48.5 cm3 47.25 cm3 It was noticeable, when looking at the results table, that the more concentrated acid had a faster rate of reaction than the less concentrated acid. This was probably because there are more particles in a concentrated acid and therefore more collisions will occur, for example; the 0.5 molar acid reactions produced on average 7 cm3 of hydrogen gas in the first 30 seconds, whereas the 1.5 molar acid reactions produced on average 38.75 cm3 of hydrogen gas in the first 30 seconds. The results appear to level out at around about 48.4cm3; the concentration of the 0.5 acid reactions does not level out because we stopped the timer before the reaction had time to complete. I have made a graph of the average reaction rate for this experiment. The numbers along the bottom indicate time; the numbers along the side indicate cm3 of gas produced. The graph supports my original prediction, it shows that the higher the concentration of the acid in molars the faster the reaction occurs and hydrogen is produced quicker, therefore I can deduce that In a higher concentration there are more acid particles to react with the magnesium ribbon and therefore it is dissolved faster. Therefore if you increase the concentration of the acid you are introducing more particles into the reaction which will in turn produce a faster reaction because there will be more collisions between the particles which is what increases the reaction rate. If we would have carried on the practical for a longer time the 0.5 molar reactions would have eventually levelled out at about 48.4cm3. While performing the experiment I had to ensure that the temperature was kept constant throughout, because varying temeperature will vary the results, if the temperature increases from the start time to the finish time then the reaction speeds will get quicker at a slightly greater rate, there was also the issue of room temperature which we measured but could not do much about because the room is a large environment and has many sources of heat. The reaction could have been sped up or slowed down in many ways but the amount of hydrogen produced remains constant. There are always ways to improve an experiment like this, I could have measured the temperature of the acid to make sure that it all started at the same temperature, and could have recorded temperature results while doing the practical too, so that I have 2 sets of results for each experiment, and could compare these and analyse how they are relevant to the experiment. Also the measuring of the acid could have been improved using small measuring syringes, and the measuring of the hydrogen produced could also be improved using the gas measuring syringe which would have produced much more accurate results because getting the upturned measuring cylinder in water without letting air in was difficult and the reading of the measuring cylinder could have been improved using the gas measuring syringe because the results would have been more accurate. Also weighing the magnesium ribbon, and cutting it more precisely would have helped get more accurate results, the magnesium was also covered in a white powder, some pieces more so than others, this is magnesium oxide, produced where the magnesium has been exposed to air, the pieces with more magnesium oxide on them would have less magnesium to react with the acid and the oxide may slow the reaction by getting in the way, or reacting with the acid and producing water. I could have cleaned each piece of magnesium with some emery cloth to reduce the magnesium oxide. I could have also tried varying other constants in my experiment, beginning of the year I temperature, the presence of a catalyst, the surface area of the magnesium or the pressure of the reaction chamber. These differentials in the variables would affect the reaction rates in different ways, but the tests all followed the same predicted pattern and shows that there is a level where all the magnesium is depleted, if we had used more magnesium and less hydrochloric acid we could have found a point where the amount of hydrochloric acid levels out before the magnesium, but we would have to use a lot of magnesium because using a small amount of hydrochloric acid would make it much harder to measure the results with current equipment. I also did some extra tests using 3 cm pieces of magnesium, and measuring how much gas was produced, to do these measurements we used the same equipment apart from the measuring cylinder which was replaced with the gas measuring syringe, the measuring syringe was much more accurate than the cylinder, and gave us better readings. The amount of gas produced from the 3cm piece of magnesium levels out at a point of 32 cm3 if we put this in a line graph with the maximum amount of hydrogen produced from the 5.5 cm pieces of magnesium we can predict how much the most amount of hydrogen that can be produced by a reaction between a different length of magnesium with hydrochloric acid. Here is a graph of the readings I got using the 4 cm piece of magnesium. Time 0.5m 1m 1.5m 2m 30 - 0:30 8 12 27 29 60 - 1:00 12 17 33 31 90 - 1:30 17 25 34 31 120 - 2:00 19 28 34 31 150 - 2:30 23 33 34 31 180 - 3:00 26 35 34 31 210 - 3:30 28 35 34 31 240 - 4:00 30 34 34 31 the results are much more varied in these tests, this could be due to greater accuracy and being able to note these variances, or from some sort of contaminant, the average amount of gas produced for a 5.5 cm piece of magnesium was 48.4 cm3 the average amount of gas produced for a 3 cm piece of magnesium was 42 cm3 the more magnesium means there are more magnesium atoms to react with the hydrochloric acid molecules and therefore more hydrogen is produced, if we put these in to a line graph we can use it to estimate how much hydrogen would be produced by other lengths of magnesium. I have drawn a line of best fit between the two points, with this graph we can estimate how much hydrogen would be produced if we reacted 1cm of magnesium. The graph gives a reading of around about 18 cm3 of hydrogen gas produced, if I had extra time we could test this theory, but unfortunately we do not. I also only did one set of results for the tests with the gas syringe, if I would have been able to continue this experiment further I could have produced more average results and seen if my predictions for the 1 cm piece of magnesium was correct. We could have also varied the concentration of the acid more so, and used less or more acid to get more accurate results or results for different test situations, instead of changing the strength we could have changed the amount of acid, or the temperature of the acid, or try varying these together and see how they effect each other.   

For this investigation I am reacting magnesium ribbon Mg with Hydrochloric acid HCl I am measuring the rate of reaction between the two, and to do this am measuring the hydrogen given off by the reaction. Magnesium is a shiny silver coloured metal, an element with an atomic...

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I am measuring the... 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   

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...

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