Rates Of Reaction Sodium Chloride

+ Sulphur + Sulphur Dioxide + Essay, Research Paper Planning This investigation is about rates of reaction and what affects them. In this case I am going to look at hydrochloric acid and sodium thiosulphate which is a precipitation reaction. They react as in the equations below: sodium thiosulphate + hydrochloric acid -> sodium chloride + sulphur + sulphur dioxide + water Na2S2O3(aq) + 2HCl(aq) -> 2NaCl(aq) + S(s) + SO2(g) + H2O(l) A reaction will only occur where the particles of the reactants meet and combine. This is called the collision theory. Therefore it stands to reason that to increase the rate of reaction it is necessary to cause more particles to collide harder and make it happen more often. There are several ways to do this and these make up the variables for this experiment. They are listed below along with predictions as to their affect on the reaction. Increasing the pressure. By reducing the volume in which the same amount of particles exist the pressure is increased. Once the same number of particles are in a smaller area there is less space in which to move and so the particles are more likely to hit each other. It is therefore possible to predict that increasing the pressure will result in an increase in the rate of reaction. I will not test this variable because the school doesn’t have the facilities to test it. However pressure is a continuous variable. Using a catalyst is another method I could use. A catalyst is a separate substance which speeds up a reaction. After the reaction has happened it gets left behind. This makes this variable unsuitable for the type of experiment I am going to do. A catalyst is also a discontinuous variable with only one likely useful catalyst emerging. Energy. By giving the particles extra energy they will move faster. This means that they cover more ground and are therefore more likely to hit each other which in turn makes the reaction faster. The best way to give energy to a particle is as heat and so I can predict that raising temperature will increase the rate of reaction. This is a continuous, independent variable. I shall test this variable – see below. I predict that temperature is proportional to rate of reaction. Concentration. Just as increasing the pressure will increase the number of particles colliding, so will the concentration. By putting more particles into the reaction, the chance of them colliding increases and so the rate increases. This variable is continuous and independent. I shall test this variable. I predict that by doubling the concentration of the acid, the rate of reaction will double. Surface area. Particles can only collide when the two sorts can meet. Therefore a reaction can only occur on the surface of the material. Therefore by increasing the area of the material which is available to collide the speed of the reaction will increase. I predict that doubling the surface area will double the speed of the reaction. This variable is continuous but I shall not test it because it is hard to control the exact surface area of the two reactants as they both come in an aqueous solution. I am going to test the two variables concentration and temperature. Both of these are independent, continuous variables. I think that concentration will have the biggest affect because the reaction is exothermic. Therefore even while I am testing concentration, heat will be given out by the reaction which will give more energy to the particles and so cause them to reach their activation energy sooner. In addition to this, looking at the original equation, it becomes clear that for every one mole of sodium thiosulphate, you need two moles of hydrochloric acid. Therefore increasing the number of hydrochloric acid particles will have a greater effect than if one were to increase levels of sodium thiosulphate. I think that both concentration and energy are proportional because: · doubling the number of particles doubles the probability that they will collide and · doubling the speed at which these particles travel will double the distance they can travel in a set time and so double the probability of them colliding. This proportionality can be expressed using algebra thus: X’ = XY’ / Y To carry out this experiment, I will need the following equipment: A3020 computer, light sensor, beaker, distilled water, sodium thiosulphate, hydrochloric acid (stock bottle), electronic scales, thermometer, burette, light, black paper, bunsen burner, tripod, mat. Firstly I shall test the variable "concentration of HCl", testing five different strengths. I shall set up the equipment as in the diagram below completely surrounding the light sensor with paper to ensure that the only light which reaches it passes through the beaker containing the reactants. As the reaction progresses, the sulphur will collect in the water and form a cloudy solution. As more sulphur is formed, less light can get through the solution and reach the sensor. I will put the hydrochloric acid into the beaker and prepare the computer. I shall then put the sodium thiosulphate into the beaker and start the computer reading. The computer records light levels as a percentage of original levels against time and is much more accurate than using a stop watch. I shall allow the reaction to take place for 60 seconds. I shall then use the computer’s accurate analysis facility to record how long it took for light levels to fall to 60% of the original. Often one of the possible weaknesses in an experiment such as this is that the different concentrations of acid are often made up inaccurately. To solve this problem I shall use one large bottle of 0.5 molar hydrochloric acid and use distilled water to dilute it to different concentrations: 20, 40, 60, 80, and 100% acid. Because I need 20ml of acid and 20ml of sodium thiosulphate I shall use varying quantities of water. For example, when making 20% concentration, I shall mix the water and acid 16ml/0.25ml respectively. After the experiment, I shall be able to draw a graph comparing concentration and reaction time. If my prediction is correct, the graph will be proportional. I shall back up my results for this section by using results generated by another group using the optical method outlined in the plan for the second variable below. I conducted the experiment as per my plan, although I had to disregard the first few computer results as the system took a while to configure. However I did several things to ensure the accuracy of my project. These included: · Washing out the glassware with distilled water before use and between measurements. This was designed to prevent any foreign ions getting into the solution as this could damage the results. · Using an analogue thermometer when heating the hydrochloric acid as this enables me to be more accurate than with a digital thermometer. · Using a small measuring cylinder and funnel when measuring out hydrochloric acid, water, and sodium thiosulphate rather than using beakers. The results for the first variable are displayed in Table 1 below. There was only time to take measurements once for each concentration as other groups needed to use the computer. However because the computer is very accurate and because I also took results from another group, this will not pose too great a problemConclusions Before I can represent my data in graph form and then test my prediction, I have to look at the way the data is laid out. I predicted that both variables would be proportional. This implies that as temperature goes up, time taken goes down. However because reaction time goes down, reaction rate is actually increasing. The best way therefore to represent the results in graph form is to draw a graph of concentration/temperature against the reciprocal of the time taken. Graph 1 shows concentration against the reciprocal of the time. However it is clear that it is not a straight line graph but rather a curve, gradually getting steeper as molarity increases. It is clear that my prediction was wrong and that the graph is not proportional. I can further test this by running my results through the formula for proportionality. X’ = XY’ / Y so X’ = (0.056 x 60) / 20 = 0.168 If my prediction was correct the reciprocal of time taken for 60% concentration should be 0.168. In fact it is 0.09. The slow growth of the graph followed by a massive increase can be explained by looking at activation energy. All of the reactions happened at room temperature (about 210C). Clearly this energy was only enough to push some of the particles beyond their activation energy. However because the reaction is exothermic it gives out energy and this energy pushes more particles to activation energy and these in turn release more heat. More particles of HCI available to reaction with the sodium thiosulphate means more heat given out and more particles being pushed to activation energy. The investigation could have been improved by testing the temperature variable on the computer as the stop watch I used could not cope with the speed of the reaction. It would also have helped to test each concentration more than once to ensure that the results were true. When using the light sensor I should have covered the underside of the sensor with black material rather than sticking on paper as this could have let in some light. In addition I should have used an artificial source of light as the natural light in the room was constantly changing as clouds pass in front of the sun. I could also have used a burette to measure out the reactants although the measuring cylinder was quite accurate. Squash Ball experiment"Squash Ball Experiment Input Variables: Pressure Of Air in Ball Type Of Surface Height Of Drop Temperature of Ball Material of Ball Acceleration Due To Gravity Mass Angle Of Surface Air Resistance Diameter of BallOutcome: Height Of BouncePrediction??????????????? The squash ball will bounce higher as the temperature gets warmer. This is because as it gets warmer the atoms in the ball vibrate more. This means that when it hits the ground the atoms push each other way forcing the ball to bounce higher. When the temperature is lowered the opposite occurs because the atoms have less energy and therefor push each other further away. The graph would look like this:The graph begins to level out because parts of the ball begin to melt at certain temperatures as the atoms get more energy and break their bonds turning the ball into a liquid. A theory, which links into this experiment, is the kinetic theory. This is because the kinetic theory deals with atoms vibrating as they receive more energy and they then break their bonds. This is linked to this experiment as the squash ball’s atoms get more energy and vibrate more before breaking their bonds to become a liquid when the ball hits a critical temperature. I don’t think the graph will go through 0,0, as even when the ball is at 0 degrees it will still bounce. I am using a large range of results as well. DiagramMethod??????????????? We set up the apparatus as shown in diagram and then heated the ball to a set temperature. We then dropped it from 70 cm high and measured the bounce. We then repeated that temperature another 4 times to gain an average. We had to be careful with the Bunsen burner and so we wore goggles. To keep the experiment fair the only thing, which we changed each time, was the temperature. We used the same ball through out the experiment and checked the ball was at the same temperature each time. We dropped it onto the same table from the same height as well. The range of temperature we used was from 5 degrees Celsius to 70 degrees Celsius. Some of the results needed to be repeated to make sure that they were accurate.ResultsTemperature (c)??? Measurements (Cm) ??????????????? Result ???? 1???????? Result ??? 2????????? Result ??? 3 ???????? Result ???? 4???????? Result ???? 5???????? Average 5????????????? 10??????????? 11??????????? 13??????????? 12??????????? 11??????????? 11.9 10??????????? 15??????????? 21??????????? 20??????????? 19??????????? 13??????????? 17.6 20??????????? 20??????????? 23??????????? 21??????????? 26??????????? 24??????????? 22.8 30??????????? 25??????????? 29??????????? 26??????????? 26??????????? 23??????????? 25.8 40??????????? 21??????????? 21??????????? 22??????????? 26??????????? 28??????????? 23.6 50??????????? 30??????????? 30??????????? 29??????????? 28??????????? 25??????????? 28.4 60??????????? 31??????????? 33??????????? 32??????????? 35??????????? 36??????????? 33.4 70??????????? 37??????????? 31??????????? 33??????????? 35??????????? 37??????????? 34.6 ?Conclusion??????????????? From my results I can conclude that as the temperature of the ball rises the height of the bounce gets higher. This is in line with the kinetic theory, which defines that as the ball gets hotter the atoms get more energy and vibrate more. When the ball hits the surface then the atoms are pushed together and because they are vibrating more they push each other further away causing the ball to bounce higher. In this experiment the kinetic theory only lasts for a specific set of temperatures. This is because when the ball hits a certain temperature it starts to melt. At 0 degrees Celsius the ball will still bounce as the atoms are still vibrating. The graph proves that the theory works for this experiment, as it is a straight line to start with. However as the ball gets nearer the critical temperature the extra height it bounces becomes less and less. This is shown as the graph levels off. The sketch graph I drew in my prediction matched the real graph showing that the science I used to explain my prediction was correct.Evaluation??????????????? Looking at my results I can say that they were quite reliable and accurate. I had one anomalous result even after an average over five measurements. I can say that looking at my results when I repeated results they were quite close together. I think that I did the experiment quite well although I found it hard to spot where the ball bounced too. This is why I did an average over 5 measurements. To improve the experiment I would need to use specialist equipment like lasers so I could be sure where the ball bounced too. Ways in which I could extend this experiment are to use a different kind of rubber in the ball so that it doesn’t melt at such a low temperature this way I could carry on to see whether the kinetic theory is still right at higher temperatures. Also I would like to see what happened when the ball was at 0 degrees Celsius. I would like to do this to see whether the atoms still vibrated causing the ball to bounce. If it did I would like to carry on getting lower and lower to see whether there was a temperature where the atoms no longer vibrated (Absolute Zero)