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Sodium Thiosulphate Investigation

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Problem. When hydrochloric acid is added to clear sodium thiosulphate solution the mixture turns cloudy and you can no longer see through it. Investigate any one factor, which influences the rate of reaction. Background Knowledge. If a chemical reaction occurs, the particles, which combine need, to meet up with each other, in other words they collide, so they can swap or share electrons. A chemical reaction can only occur between the particles when they: 1) Collide with each other. 2) Have enough energy to react. If there is little energy they will bounce off each other. Diagram on the next page to show particles colliding. What Factors affect the rate of reaction? Increasing Temperature: This means that the particles will move faster, therefore the collisions will be harder, as there is more energy. The minimum energy of a collision for a reaction to happen is called the activation energy. ...read more.


As I decrease the concentration of sodium thiosulphate, I will decrease the rate of reaction. As there are less particles of sodium thiosulphate, this will result in less collisions taking part. Observations and Measurements. I will use 50mls of 5 different concentrations of sodium thiosulphate solution. These are: 0.050 0.075 0.100 0.125 0.150 For each of the above concentrations I will time how long it takes for a reaction to occur. Apparatus. Paper marked with Dropper. X. Conical Flask. Measuring Cylinders. Stop Clock. Steps to carry out Experiment. 1) Measure out 50mls of sodium thiosulphate solution into a conical flask. 2) Place the flask on top of a piece of paper with an X drawn on it. 3) Add 5mls of hydrochloric acid to the flask and start stop clock immediately. 4) Time until the cross is no longer visible through the solution. ...read more.


I know that my results are accurate as I carried out an experiment for each of the concentrations 3 times and then took the average. I took great care when measuring out the volumes of acid and sodium thiosulphate. I also used the same 'X' and ensured that the same person looked through the solution to see when the reaction was over. All of the above ensured a fair test. If I were to do this experiment again I would uses burrettes for measuring the volume of sodium thiosulphate and the acids. The reason why I would use these is because they are more accurate than measuring cylinders. In conclusion when the concentration of sodium thiosulphate was 0.050 the time taken for the reaction was 222.7, this is a low concentration and therefore it took a long time for the reaction to occur. When the concentration of sodium thiosulphate was 0.150 the time taken for the reaction was 0.48, this is a high concentration therefore if did not take long for the reaction to occur. ?? ?? ?? ?? ...read more.

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