How concentration affects the rate of reaction between Hydrochloric Acid and Sodium Thiosulphate

How concentration affects the rate of reaction between Hydrochloric Acid and Sodium Thiosulphate

Chemistry Coursework

How Concentration Affects a Reaction

Aim:

The aim of this experiment is to find out how concentration affects the rate of reaction between Hydrochloric Acid and Sodium
Thiosulphate.

Introduction:

This experiment will be carried out by drawing a cross on a piece of paper and mixing hydrochloric acid and sodium thiosulphate together to see if the cross disappears. The concentration of hydrochloric acid would change every reaction to show that concentration effects a reaction. The time in which the cross took to disappear would be recorded as well as the temperature at the start and end of the reaction, the concentration of the hydrochloric acid and the amount of hydrochloric acid and sodium thiosulphate used.

Sodium Thiosulphate + Hydrochloric Acid ------------> Sodium Chloride
+ Water + Sulphur Dioxide + Sulphur

Na2S2O3 + 2HCl 2NaCl + H2O + SO2 + S

Preliminary Work:

The problems that arose whilst doing the preliminary experiment was that the beakers and measuring cylinders were not cleaned out properly and some of the sodium thiosulphate turned cloudy were there was previously hydrochloric acid inside the beaker.

The preliminary experiment showed that concentration effects the rate of reaction as well as the temperature does. The higher the concentration of hydrochloric acid, the faster the reaction was because the more particles there were to collide and break old bonds and make new bonds. Also if the temperature was higher the particles would move around faster because they have more energy and would also cause more effective collisions.

GRAPH

Fair Test:

The experiment will ...

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... anomalies within the experiment and this may have been caused by the stirring or the timer being started and stopped wrongly. I think that our group had a good method because our results showed what we were trying to find out, which was to test how the change of concentration affects a reaction. To get rid of any anomalies we could have either not stir the mixture or use a machine to stir it at the same speed each time. I think that the procedure that we had used was adequate to test and that it was reasonably reliable. In my prediction
I had stated that as the concentration increases, the time taken for a
10% decrease in light intensity would decrease. This is because more particles would be in the higher concentration causing more effective collisions to happen. In future experiments we could increase the range of results as well as having more intermediate values.