I plan to display my results in a table, which will look like this: -
Our range of the amount of sodium thiosulphate used will go between 1ml and 50ml. This is so we can get more reliable, accurate results, with out it taking to long, and it will prove or disprove that if you double the concentration, then the rate of reaction will also double. We will do each experiment 3 times and put our results in the table above.
When using hydrochloric acid, we should remember that it is irritable to the skin and you should always wear safety goggles. Also sulphur dioxide is toxic, and can be corrosive.
When using it use should follow these safety instructions: -
- Use the smallest volume possible
- Wear eye protection
- Keep hair tied back
- Remain standing with bags and stools tucked under
If sulphur dioxide does get in your eye, flood eye with tap water for 10 minutes then see a doctor. If it is spilt on floors/ benches, Wipe up small amount, or for large amounts open windows cover with mineral absorbent, scoop into bucket and add water.
Before doing the experiment I did some preliminary work so I had a good idea of what amount of sodium thiosulphate I should use and the amount of time it would take, because I only had a limited amount of time of two lessons to complete the experiment. My results were that with 1ml of sodium thiosulphate and it would take about 40 seconds to complete. This gave me a good idea of the time different I also did the same for my maximum mass, and I knew that as it took more than half an hour but though it would be finish within the lesson, but we would have to set three of at a time and work fast to get all of the experiments done in time. My results from my preliminary work also show how well my experiment will work.
Considering Evidence
My hypothesis was that if you double the concentration, the rate of reaction would also double, and as my graph shows strong coloration between rate of reaction and concentration, so it is directly proportional and if you double the amount of concentration then the rate of reaction will also double. On my graph it works but because there a measurements that are slightly above or below the mass, it is hard to average them out correctly. Overall my results were very consistent and look reliable, as nearly all my points fall on the 45-degree angle of my line of best fit is a positive direction.
This is consistent with the collision theory, which happens for a chemical reaction to take place, particles must collide with sufficient activation energy, the rate of reaction depends on the frequency of the collision, the more frequent the collision, the faster the reaction, so the more energetic the collisions are, so the reaction will take place much faster. So if you double the frequency, the speed of reaction will also double.
In the evidence these is a trend that if you double the concentration, the rate will also double. This is shown on my graph by the dotted lines. The results are shown in the table below: -
The concentrations above are done from the second ‘y’ axis, as all my results are consistently wrong, I have work out that the axis would make much more sense and prove my predict correct. This shows that in conclusion, if you double the concentration the rate of reaction times 1000 will almost double exactly as well, because of the collision theory, this means that there is more chance of a sodium thiosulphate molecule hitting and reacting with an acid molecule, therefore increasing the rate of reaction and decreasing the time it takes to do so.
Evaluating
Overall my results were accurate and showed that if you double the concentration then the rate of reaction would also double. In doing this experiment I have collected 15 pieces of data within that there is one anomalisms point (see graph) my 15 results, most of which are close to the line of best fit except my anomalisms point, this makes them reliable as well. This anomalies point could be because of a number of things, it could have been to little water, too much sodium throsulphate or I may of not stop the time at the precise moment the cross disappeared, I could of stop it, too early.
When the concentration was 26.7 g/dm3 it was very accurately done as the 3 points on the grape are close together. Whereas at 20 g/md3 it is less precise as the crosses are further apart. This is due to an equipment error, changing the spread of the crosses. Form my 15 results I think I can say that these support my conclusion as I only had 1 anomalisms point and I have seen 6 other groups results of this test and they have come out with similar results.
While doing this experiment, the equipment I used was sufficient enough to come to a sensible conclusion, but the temperature wasn’t the same as we did it over 2 days, if it was they would be even more accurate, as when the temperature went up the particles in the mixture will move more quickly, the particles will collide with each other more often, with greater energy and many more collisions will be successful. So the higher the temperature, the rate of reaction is faster, as it went up by only 0.5 of a degree, so shouldn’t of made too much difference, but when heating the liquid, so it rises by 10o, which is a small increase it would of caused a large decrease in the time taken for the reaction to end.
The concentration I was told would be 40 g/dm3 but isn’t as you can see from my graph other wise it would have gone through 0. Something might have been added to it at the beginning of the lesson that has changed it, as the concentration leading to all the results being out by the same amount, also happened to other groups and could of easily been contaminated by put something back into it, after doing an experiment they could of pour the liquid back into the container, or while the lab technician was measuring the concentration out she could of easily added to much or too little water, so it wouldn’t go through ‘0’.
