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How Does The Concentration Of Sodium Thiosulphate Affect The Rate Of Reaction

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How Does The Concentration Of Sodium Thiosulphate Affect The Rate Of Reaction? Aim: In this investigation I'm going to look at how the factors that affect the rate of reaction can alter the speed of a reaction. There are five factors which affect the rate of a reaction, according to the collision theory of reacting particles. These are: > Temperature. > Surface Area. > Introduction of a catalyst. > Pressure (in gases). > *Concentration (of solution). The factor that I will base my experiment around is the concentration. I will use this because it is the most practical to investigate, it would take longer to prepare a solid in powdered or solid form, and it is difficult to get accurate readings due to the unpredictable mistakes of human errors, and as gas is mostly coluorless it is difficult to gauge a reaction changing the pressure, and if a substance is added to give the gas color, it may influence the outcome of the experiment. Similarly the use of a catalyst complicates things, and if used incorrectly could alter the outcome of the experiment. (Explain this) The Collision Theory: * Molecules are found in constant random motion. * When two molecules collide they may interact. * Anything that increases the number of collisions increases the number of productive collisions. The main basis is that a chemical reaction will occur when two molecules collide together with energy greater than activation energy. The way a chemical reaction happens can be influenced by different factors. The first being temperature. The molecules will be heated and given more energy. This means they will move around faster and will increase the collision frequency. Also when they collide they will impact with more force. Therefore the activation energy should be overcome and a reaction produced. Surface area is also another factor. If there is a greater surface area, there will be more area for the molecules to collide on. ...read more.


I then added 20ml of Sodium Thiosulphate to make the total solution volume of 30ml as said. Because this was the first experiment water was not required. When this was completed I steadily poured the reactants in the two measuring cylinders into the empty conical flask which was placed on top of the penciled cross. As soon as the two reactants had contact with each other, I instantly started the stop watch. At this point everything was going well, the time was ticking away and the Sulphur was nicely forming making the solution go translucent, but I was waiting for the solution to go completely opaque so the cross was no longer visible, I kept a birds eye view of the solution reacting but making sure that the safety goggles were on at all times, I figured having a view from top would give me a more accurate time as I would have a better view of the cross. When I saw the cross become totally covered with the solution I instantaneously stopped the stop clock and recorded down the time on my results table. When that phase was completed and I had the time recorded I removed the contents of the conical flask, washed it and dried it, as this was one of the fair testing steps. After I was ready to restart the process I this time added 17ml of Sodium Thiosulphate, 10ml of Hydrochloric acid but because the total had to add up to 30ml I added 3ml of Water to the Hydrochloric acid this was to lower the concentration of the Sodium Thiosulphate when it was mixed in the conical flask. The same was repeated as stated before after the two solutions were mixed. I recorded the time after the cross was entirely covered. This was again repeated several times after, each time adding different amounts of Sodium Thiosulphate and Water but still keeping to the equal 10ml of Hydrochloric acid. ...read more.


I tried my best to keep the experiment as fair as possible but maybe a few uncontrollable factors could have tampered with my results, this could include small drops of water being left at the bottom of the conical flask after I had washed it out, this I could be unaware of and the next time when I added the solution again it could slightly reduce the concentration which slightly then alters with the results. This would be unfair but not knowingly attended. Luckily this did not affect my overall results and did not cause any anomalies. Improvements: The experiment was handled fairly but it could have been even fairer. Because the reaction was finished when the cross on the pad disappeared and this is only seen by the naked eye. With the whole class doing this with different eye types, there is no exact fairness in the experiment. Fairness in this issue can be found by using devices such as a light sensor. The light sensor will pass through the flask, of were a reaction is taking place to a receiver. When the light sensor can not reach the receiver, the timing will be stopped automatically. This will bring fairness to experiments to test all similar to rate of reaction. Apart from this minor things like using a different conical flask each time, to assure that no extra Water or left over solution is left at the bottom of the flask, and maybe using devices such as burettes, which wouldn't make much of a difference. (Also repeat the experiment several times) Finalizing this investigation I believe I have accomplished my mission by proving my prediction, collected a reliable set of results and drew up an accurate graph. I have also managed to write a detailed method, analysis and evaluation to this investigation which is probably the most hard and testing parts of this coursework. ?? ?? ?? ?? 1 Ali Ilyas Chemistry C/W 10F Triple Science ...read more.

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