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An experiment to investigate the effect of changing the concentration of hydrochloric acid on the rate of reaction with sodium thiosulpahte.

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Introduction

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. 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. ...read more.

Middle

* Draw a cross on a piece of paper and place the conical flask on it. * Measure out 10ml of acid and add it to the conical flask and start timing. * Look into the top of the conical flask and when the cross can no longer be seen stop the stop watch. * Do the experiment again but measure out 8ml of hydrochloric acid. Then add 2ml of distilled water. The ratio for each experiment will therefore be 10:0, 8:2, 6:4, 4:6 and of acid to water Conclusion I conclude that whilst carrying out this investigation I found out that the more acid was in the solution the cross on the paper disappeared quicker. This shows that the more concentrated the acid is then the quicker the reaction time. My research about the collision theory was correct and the more concentrated the solution is then the number of collisions will be increased. If the numbers of collisions are increased then the reaction time will also be increased. My prediction 'that the less concentrated the acid is then the longer it will take for the sodium thiosulphate to react with ...read more.

Conclusion

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. This would make the results more accuarate. ...read more.

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