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Rate of Reaction - Sodium Thiosulphate and Hydrochloric Acid Coursework

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Introduction

Rate of Reaction - Sodium Thiosulphate and Hydrochloric Acid Coursework Aim Investigation, to find out how the rate of reaction between Sodium Thiosulphate and Hydrochloric acid is affected by changing the concentration. Introduction I must produce a piece of coursework investigating the rate 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 development of a product during a chemical reaction. It is measured by dividing 1 by the time taken for the reaction to take place. There is five factors which affect the rate of a reaction, according to the collision theory of reacting particles: temperature, concentration (of solution), pressure (in gases), surface area (of solid reactants), and catalysts. I have chosen to investigate the effect of concentration on the rate reaction. This is because it is the most practical to investigate. Dealing with temperatures is a difficult task especially when we have to keep constant high temperatures. Secondly the rate equation and the constant k changes when the temperature of the reaction changes. We have no gases and solids involved therefore it is easy to deal with solutions. Similarly the use of a catalyst complicates things, and if used incorrectly could alter the outcome of the experiment. The theory behind this experiment is that 'Increasing the concentration can increase the rate of the reaction by increasing the rate of molecular collisions.' The equation for the reaction is: Sodium Thiosulphate + Hydrochloric acid ----> Sodium Chloride + Sulphur Dioxide + Sulphur + Water Na2S2O3(aq) + 2 HCl(aq) ----> 2 NaCl(aq) + SO2(g) + S(s) + H2O(l) I will place the reaction mixture on a paper with a black cross-drawn on it. When the cross is completely obscured, the reaction will have finished. The time taken for this to happen is the measure of the rate of reaction. ...read more.

Middle

(We had to add the Sodium Thiosulphate and the water at the same time for this to be a fair test also). We then recorded the time for the cross to become completely obscured. We repeated this many times, adding different amounts of Sodium Thiosulphate and water each time, and recording the time taken each time. Results Table of results Table 1 Na2S2O3(aq) HCl(aq) H2O(l) Time (cm3) (cm3) (cm3) (Seconds) 50 5 0 48.85 45 5 5 45.46 40 5 10 51.06 35 5 15 59.84 30 5 20 109.04 25 5 25 115.27 20 5 30 161.32 15 5 35 219.08 10 5 40 312.53 5 5 45 459.47 Table 2 Na2S2O3(aq) HCl(aq) H2O(l) Time (cm3) (cm3) (cm3) (Seconds) 50 5 0 45.07 45 5 5 46.99 40 5 10 48.10 35 5 15 57.67 30 5 20 89.17 25 5 25 107.45 20 5 30 134.61 15 5 35 179.81 10 5 40 234.84 5 5 45 347.21 Table 3 Na2S2O3(aq) HCl(aq) H2O(l) Time (cm3) (cm3) (cm3) (Seconds) 50 5 0 47.29 45 5 5 48.04 40 5 10 52.17 35 5 15 58.76 30 5 20 107.88 25 5 25 114.09 20 5 30 142.52 15 5 35 221.26 10 5 40 310.33 5 5 45 469.27 I have also come up with a set of average results for all 3 experiments: - Average Results Table Concentration Na2S2O3(aq) HCl(aq) H2O(l) Time (M) (cm3) (cm3) (cm3) (Seconds) 1 50 5 0 47.07 0.9 45 5 5 47.10 0.8 40 5 10 50.77 0.7 35 5 15 58.76 0.6 30 5 20 102.63 0.5 25 5 25 112.27 0.4 20 5 30 139.48 0.3 15 5 35 219.71 0.2 10 5 40 285.03 0.1 5 5 45 418.65 After collecting the results I will be in position to analyse and use graphical format to evaluate the results. When the results are collected there are two methods that could be adopted to find the order of the reactants in order to find the rate equation. ...read more.

Conclusion

Carrying out the experiment in a chemist lab which has more detailed technology available will make the experiment more reliable, accurate and will minimise the errors. I conclude that the more concentrated a reactant is, the quicker the rate of reaction time will be.I have come to this conclusion because of several reasons. Firstly, my results give conclusive evidence that as the amount of Sodium Thiosulphate decreases and the amount of water in the solution there are less atoms to collide and therefore less successful collisions causing chemical change so the reaction rate is slower. In a more concentrated solution, there are more atoms to collide so the reaction time is quicker. Overall I think that this experiment was a success as I have proved that concentration does affect the rate of reaction, and I have also found that when the concentration is doubled the rate of reaction is not necessarily halved. I think I could have improved my investigation by: * Obtaining more results to get a better overall result. * Take times for a lower concentration than 5cm3 (we could not due to time restrictions). * I used ICT to display my coursework, but I did not use it in anyway that affected the experiment. * I would like to do a further experiment to confirm my results. However I am restricted by time and the available facilities which means I cannot repeat it. * Also instead of using a cross on a piece of paper I could use a single beam of light until it could no longer be seen * Use of computer to aid analysis of results * Carry out all of the experiments on same day to improve accuracy * Calculate more than ten tangents to improve accuracy List of sources to aid work Various Textbooks and Internet sites were used in providing background information. Cambridge Chemistry 2 Book - Brain Ratcliff, Helen Eccles Do Brilliantly at ... A2 Chemistry- George Facer Chemistry A-Level through Diagrams- M. Lewis http://www.chemguide.co.uk/physmenu.html#top http://www.chemguide.co.uk/physical/basicrates/arrhenius.html Shamas Hussain 01/05/2007 Mrs Edmonson B1 1 ...read more.

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