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Rates Of Reaction -How The Change Of Concentration In Sodium Thiosulphate Affects Its Reaction Rate

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Joe Barrick 11BUN April, 2005 Rates Of Reaction - How The Change Of Concentration In Sodium Thiosulphate Affects Its Reaction Rate Introduction In my experiment I will investigate how the rate of reaction of Sodium Thiosulphate will be affected by the change in its concentration. But before this I carried out a trail experiment to see which solution, Sodium Thiosulphate or Hydrochloric acid would be more suitable. My Trail Experiment Method was to first collect all of the equipment needed, then I measured out the right amounts of each solution by measuring from the bottom of the meniscus. Then I put the solutions into a conical flask and timed how long it took for the paper cross underneath the flask to disappear. I tested both solutions by changing the concentration of one, then of the other but I kept the total volume the same. I repeated the experiment again to make my results more accurate, these were my results: Volume of Sodium Thiosulphate (cm3) Volume of Hydrochloric Acid (cm3) Volume of Water (cm3) Time Taken 1st (seconds) Time Taken 2nd (seconds) Time Taken Average (seconds) 10 10 20 15 20 15 10 10 0 5 0 5 67 66 38 57 74 60 39 61 70.5 63.0 38.5 59.0 My Prediction I predict that the more concentrated the Sodium Thiosulphate is the quicker the reaction will take place. ...read more.


The Stop Watch - To time the reaction. Safety Goggles - To protect eyes. Waste Beaker - To put the waste products in. My Method For Actual Experiment I first got all of the equipment listed above, then I measured out 35ml of Sodium Thiosulphate and 10ml of Hydrochloric Acid. I then put the paper cross underneath the conical flask. I then put both the solutions in the conical flask and started the stopwatch straight away. I stopped the stopwatch when I could no longer see the paper cross. I then recorded the results I found in a table and I then repeated it twice and also recorded what I had found. I changed the concentration of the Sodium Thiosulphate five times but to keep the volume the same throughout I added the difference in water. The total amount of water I added was 50ml overall. So then I measured 30ml of Sodium Thiosulphate but now added 5ml of water, I measured out the constant 10ml of Hydrochloric Acid and put both solutions into the conical flask and started timing. I stopped when I could no longer see the cross and recorded my findings. I then repeated it twice more and recorded my results. ...read more.


The collision theory says that the rate of the reaction depends on how often and how hard the reacting particles collide with each other and with enough force. So my prediction agrees with the collision theory, as the solution became weaker the reaction time increased because there were less molecules and particles to collide. Evaluation I think that my experiment went well overall but with some small difficulties; these were that measuring the exact amount of the Hydrochloric Acid, Water and Sodium Thiosulphate was quite hard because the measuring cylinders aren't 100% reliable. Also you couldn't know exactly when the paper cross had fully disappeared. The stopwatch had to be started precisely at the time of when both the solutions had been put into the conical flask and stopped immediately when the cross had disappeared. If I was to redo my experiment making it better and more accurate I could use a LDR -Light, Dependant, Resistor- to assess the light in the conical flask which will determine when the paper cross can no longer be seen. I could also carry out the experiment over the same day in the same room -which will not effect the temperature- and by using a computer to calculate the correct amount of the solution. I could also perform the investigation more times to improve the range and averages of my results. But overall I think my experiment went well. 1317words ?? ?? ?? ?? ...read more.

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