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Science Course Work

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Science Course Work Rates Of Reaction Aim: My aim is to find out how the rate of the reaction between Sodium thiosulphate and hydrochloric acid changes as the concentration of hydrochloric acid (Input Variable) changes. Word Equation: Sodium Thiosulphate + Hydrochloric Acid Sodium Chloride + Sulphur Dioxide + Sulphur + Water Symbol Equation: Na2 S2 O3 (aq) + 2Hcl (aq) 2NaCl (aq) + SO2 (g) + S(s) + H2O (L) The rate of a chemical reaction is the speed at which it takes place. It can vary from a fraction of a second to several weeks, months or even years. The 3 main factors which affect the rate of a reaction are, changing the surface area of any solids involved in the reaction, changing the concentration of any reactants that are in solution and changing the pressure in reactions where gases are involved. Since I want to find out how the concentration of hydrochloric acid affects the rate of reaction between hydrochloric acid and sodium thiosulphate. Only the first two of those factors will apply to my experiment. The only factor that I will change is the concentration of hydrochloric acid. This is because the concentration factor affects the rate of the reaction in my experiment the greatest. ...read more.


Safety Precautions and Fair test The safety precautions I would take are wearing safety goggles to make sure I don't get any of the acid in my eyes. I would also take care not to touch any of the acid with my hands and not to breath in any of the sulphur dioxide produced in this reaction. Also to make it a fair test I will make sure that there is only one person looking at the cross until they cant see it anymore because of the solution turning cloudy and then stopping the stopwatch. This is because if there was more then one person looking at the cross and deciding when they cant see it any more and therefore stopping the stopwatch. Then there eyesight might be slightly better or worse then the other person that observed the cross before or would after him/her resulting in him/her being able to see the cross for slightly longer/shorter. Therefore meaning that the investigation would not be fair as the results would not be accurate, as they were not taken by only one persons judgement. Some other things that I would do to make it a fair test are that I will use the same volume of solutions in every experiment (10ml of sodium thiosulphate and 5ml of hydrochloric acid). ...read more.


I think my investigation was fair as I followed my plan exactly. And I made sure that there was only one person looking at the cross through out all the experiments, I made sure that I used the same volume of solutions in every experiment (10ml of sodium thiosulphate and 5ml hydrochloric acid). I used the same cross for all the experiments and finally I made sure that there was only one person stopping the stopwatch through out all the experiments. So overall I think keeping my investigation fair was a success and my results reflect that. I have collected enough evidence to prove that as the concentration of hydrochloric acid increases from (0.5 to 2.0) molar so does the rate of reaction, providing that the concentration of hydrochloric acid is the only input variable. But my investigation only proves that the rate of reaction increases as the concentration of hydrochloric acid from (0.5 to 2.0) molar. I could have carried out the experiment with higher concentrations of hydrochloric acid to see for how long the rate of reaction continued to increase with the concentration. If I could use higher concentrations of hydrochloric acid then I could have made a more in depth statement like "as the concentration of hydrochloric acid increases so does the rate of reaction until the concentration gets to... molar". ?? ?? ?? ?? Science C/W Rates Of Reaction ...read more.

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