After pouring the chemicals into the measuring cylinders, making sure the measurements are as accurate as we can make them, we will then pour them all into a conical flask, and with each experiment making sure each chemical is poured in, in the same order. Underneath the conical flask will be a piece of paper with a cross drawn onto it, this is to show us when the reaction has completed. To make sure it stays as a fair test the same person will be used to say when the cross disappears, as each persons sight varies. We will firstly pour in the Sodium Thiosulphate, secondly, the water, then we will stir it for five seconds and then finally pour in the Hydrochloric Acid. As the Hydrochloric Acid is poured in, we will time how long it takes for the cross to disappear. We plan to do each of the experiments three times, so we can get an average result.
Diagram
Specimen Results
(From 'Chemistry' - Hunt and Sykes)
These results were taken from the textbook 'Chemistry - Hunt and Sykes'. If the experiment is undertaken perfectly then we should results close to this.
Fair Testing
To make this a fair test we took several steps. These were mainly to control the following variables:
- Acid - Volume and concentration so that there is the same number of acid molecules each time.
- Sodium Thiosulphate/Water - The total volume of both put together is the same each time.
- Temperature - The higher the temperature the quicker the rate of the reaction will be.
- Conical Flask - If flask is a larger based then the cross will disappear sooner.
- Cross - Will disappear with thinner cross sooner.
Safety
We took several safety measures when performing these experiments.
- Firstly, we made sure we were wearing our lab coats and that they were fastened.
- Secondly, we wore safety goggles through out the experiment.
- Thirdly, we made sure we had a clear area around us to work.
Results
Our Group results
Classes Results
Specimen results ('Chemistry - Hunt and Sykes')
Analysis
My results show me that the greater the concentration the greater the rate. This therefore backs up my prediction in saying that the greater the concentration of Sodium Thiosulphate, the greater number of Sodium Thiosulphate molecules there will be. This would mean that the frequency of collisions would increase which would make the rate of the reaction speed up.
When you increase the concentration by two, the rate increases by around two, according to the classes mean results:
The Concentration = 0.045 so The Rate = around 9 seconds
The Concentration = 0.09 so The Rate = around 18 seconds
However, according to Our Groups results this compares differently:
The Concentration = 0.045 so The Rate = around 8 seconds
The Concentration = 0.09 so The Rate = around 19 seconds
