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Investigate the effect of concentration on the rate of reaction.

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Plan Aim: For my coursework investigation, I aim to investigate the effect of concentration on the rate of reaction. The Reaction which I am going to use, is that between: Sodium thiosulphate solution and dilute hydrochloric acid The chemical equation for this reaction is as follows: Na2S2O3 (aq) + 2HCL (aq) -------> 2NaCl(l) + H2O (l) + SO2 (g) + S(s) Sodium + Hydrochloric --------- > Sodium + Water + Sulphur + Sulphur thiosulphate acid chloride dioxide Research Primarily, I must summarise the key bits of information and the key theories that are relevant to my investigation. Chemical reactions Chemical reactions are processes, which leave us with new substances. In a chemical reaction, the materials, which we put in at the start, are called the 'Reactants'. These reactants are changed in the chemical reaction, into a new substance; this substance is called the 'product' of the reaction. For a reactant to change into a product, the atoms in the reactants have to be re-arranged. This re-arranging happens when the reactant particles collide with each other. In all chemical reactions there are two main changes that take place, these changes are: * The reactants have to be decomposed by breaking the chemical bonds within them, in order to allow new, different bonds to form the products of the reaction. * Once the original reactants have been broken down, new chemical bonds are formed, between all the elements, which have been released. This enables new chemical products to be produced. Reactions where energy is taken in from the surroundings are called endothermic reactions. An example of an endothermic reaction would be photosynthesis. Carbon dioxide + Water ----------> Glucose + Oxygen (Energy is taken in) Reactions where energy is given out into the surroundings are called exothermic reactions. An example of an exothermic reaction would be respiration. (We use food to supply our bodies with energy eg: carbohydrates. ...read more.


* Stop watch * Eye protection-Goggles * Water (starting with a volume of 0 and then increasing by 5 each time) * Apron Diagram Below is a diagram of how I will set up my equipment for my experiment at the moment. However, due to my preliminary series of experiments I will confirm which apparatus and what measurements to use later on. During my preliminary experiments, everything worked out perfectly so therefore, below is a list of apparatus, which I will use for the real experiment: * Sodium thiosulphate solution (starting with 40 g/l and decreasing by 5 each time) * Hydrochloric acid (acid concentration will be fixed) * 3 measuring cylinders * 1 conical flask * 1 piece of paper (to draw a cross on) * 1 stop watch * Eye protection-1 pair of goggles * Water (starting with a volume of 0 and then increasing by 5 each time) * 1 apron The diagram I provided earlier for my provisional experiments is the exact one I will use for the real experiment. Sources used To aid me with this plan I used the following sources: * School Key Science GCSE textbook by Eileen Ramsden * CGP Chemistry Revision Guide by Richard Parsons Obtaining, analysing and considering Evidence I have concluded my experiment and everything worked out to plan, and now that I have finished, below, is a list of my results, which I have gathered from completing it. I have adjusted the results of the time in the second furthest column to the nearest second and the rate of reaction to four decimal places. In order to calculate the rate of reaction, I completed the following sum: 1 time Volume of Sodium Thiosulphate (ml) Concentration of Sodium Thiosulphate (g/l) Volume of Water (ml) Volume of Hydrochloric acid (ml) Time (s) Rate of reaction (s) 40 40 0 10 26.0 0.0384 35 35 5 10 28.0 0.0357 30 30 10 10 34.0 0.0294 25 25 15 10 43.0 0.0232 20 20 20 10 ...read more.


I had collected plenty of evidence and it was as accurate as it could have been. I didn't have to repeat any results from the experiment, however, there was one anomalous result. It came from the first attempt (figure 1), which can be seen in the results section. This result had a reasonable difference compared to the other results. Nevertheless, there could be some perfectly logical explanations such as the following: * There were two other people in my group who could have measured the amount of sodium thiosulphate and hydrochloric inaccurately. * There was not enough time for the whole set of results to be collected in just one lesson. Therefore, the equipment had to be left for a few days until our next lesson. When the equipment was used again, another member of the group may not have washed the conical flask out after and before the next set of results were taken. Therefore, there may have still been some remains of sulphur from the previous set of results. * The amount of water in the test tube and beaker might have differed. * A new conical flask was used half way through the first set of results because the first one smashed. As a whole, I think that the experiment worked out extremely well. However, one way which I could have used to improve my investigation is to have recorded even more results to get a meaningful average and also to repeated the anomalous result so that I had a full set of results for each attempt. Another technique I could have used to improve my investigation would be data logging. I would have loved to extend this investigation in many ways. Firstly, I could have kept the concentration of sodium thiosulphate the same and changed the amount of hydrochloric acid to see what the difference would be compared to my results. This would have been very enjoyable. However, I did not have enough time and there was also a lack of equipment which I would have needed. -1- ...read more.

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