An experiment to investigate the effect of changing the concentration E

An experiment to investigate the effect of changing the concentration of hydrochloric acid on the rate of reaction with sodium thiosulpahte. Aim I am trying to find out how the concentration of hydrochloric acid affects the reaction time with sodium thiosulpahte. If a clear solution of sodium thiosulphate is mixed with hydrochloric acid then a reaction will occur where a creamy-yellow precipitate of sulphur is produced. H20 Text Box: + Text Box: + Text Box: + Na2S203 2HCL Text Box: + 2NaCl SO2 S Reactants Products The sulphur takes a while to form and starts to turn the water cloudy after a short time. You cannot tell when the reaction has stopped so a cross drawn on a piece of paper in pencil can be sued to do this experiment. The liquid is placed on top of the cross in a beaker and it is timed how long it takes for the cross to disappear when viewed through the liquid. This experiment can be used to investigate the effects of concentration and temperature on rate of reaction. This is the experiment I am going to do because I am trying to see how the concentration of acid affects the rate of reaction. Variables In my investigation I could change: * Concentration of sodium thiosulphate * Temperature of solution * Concentration of acid * Type of acid * Volume of thiosulphate * Volume of acid I am going to change the concentration of acid. I will keep all the other variables the same. The independent variable will change the dependant variable- the rate of reaction. Prediction I predict that the less concentrated the acid is then the longer it will take for the sodium thiosulphate to react. If you increase the temp, increase concentration, add a catalyst or the solid reactant is crushed up into smaller bits then the rate of reaction will always increase. Apparatus * Sodium thiosulphate * Hydrochloric acid * Measuring cylinder * Beaker * Paper * Pencil * Distilled water * Stop watch * Conical flask Safety Goggles should be worn to prevent any of the solution from going into the eye. Everyone should behave sensibly to prevent accidents. Collision theory The rate of reaction depends on how often and how hard the reacting particles collide with each other. The particles have to collide hard enough in order to react. The rate of reaction can be increase... ...2 and 3 only have a 1second difference in time. These results are too close together and cannot be reliable. These results aren't adequate for a firm conclusion as it has a few anomalous results and on the average times they don't have a large enough gap between them e.g. 34 and 36. The experiment should be carried out more times for a more accurate result. The procedure used was suitable but produced quite unreliable results as the cross on the paper may have not fully disappeared when the other person was told to stop the timer as this is what we did. If the person looking at the cross and observing when it disappeared changed then the person's opinion on when it has disappeared may make it an inaccurate test so it would have to be kept the same person all the time. If I did the experiment again I would probably take more time measuring out the solutions and it would probably be a better idea for the person observing to see when the cross can no longer be seen to have the stop watch so they can stop it at the exact time they can no longer see it. It could also be improved if the experiment was carried out more times as a better average could be produced.