The reaction of the collision theory:
Sodium thiosulphate+hydrochloric acid sodium chloride+ sulphur dioxide + water +sulphur
My prediction
I predict that as I increase the concentration of the sodium thiosulphate the rate of reaction will increase. This is because the number of particles will increase meaning more chance of collision further resulting in the rate of reaction to increase.
Apparatus
Conical flask
Hydrochloric acid
Sodium thiosulphate
Thermometer
Paper with cross
Stop watch
Measuring cylinder
Concentration of sodium thiosulphate
In order to change the concentration I will make up the following solutions:
2 molar =316g of sodium thiosulphate in 1000mls of water.
1.5 molar =237g of sodium thiosulphate in 1000mls of water.
1 molar =158g of sodium thiosulphate in 1000mls of water.
0.5 molar =79g of sodium thiosulphate in 1000mls of water.
0.25 molar =39.5g of sodium thiosulphate in 1000mls of water.
Method
I will wash out all apparatus to avoid cross contamination.
- Into a conical flask I will add 25cm³ of 2 molar sodium thiosulphate.
- The flask will be placed on top of a piece of paper with a pre drawn cross on it.
- 25cm³ of hydrochloric acid is added to the flask and the stop watch started as soon as the acid has been added.
- When the precipitate of sodium has formed and at the point when I can’t see the cross I will stop the stop watch and record the time in a pre prepared table.
- I will repeat these 3 times to ensure my results are accurate.
- I will then repeat this method with again with different molars again recording each result.
Result
My results in the graph have shown that the higher the concentration the more time it takes to react. This is because when there is more particles the more chance of collision.
I collected 4 results which were 0.25, 1.0, 2.0, however there was a cross contamination with 1.5 molar so we couldn’t use this solution. However there were enough results to draw a conclusion as it shows a correlation on the graph, which was a negative correlation. One of my results were an outlier this may have been effected by temperature or cross contamination so maybe I should of used a thermometer and used different apparatus rather than just washing them out each time to make it a fair test.. I repeated the test 3 times so it was a fair test however if I would do a result again I would re-do the 2.0 molar as it was abnormal.
I think my results have shown a big enough range as I have done 4 results these were enough to draw a conclusion as it shows a negative correlation on the graph.
I didn’t have no problems with my method as I repeated the results 3 times and got the average however I should have used a thermometer as the temperatures could have been different effecting my results. However I did measure the thiosulphate and the acid as if I didn’t there would be more particles meaning more chance of collision. And my results were very precise as I used a stopwatch which meant the time was accurate unlike if I counted the time myself. The readings for the reaction was fairly accurate however it could be improved by using a light sensor what meant we would know the exact time in which we couldn’t see the cross.