The effect of concentration
The concentration of reactants in a solution can affect the rate of chemical reactions. The higher the concentration, the faster the reaction will be. For example if I was to add a extra 50cm3 of Na2S2O3 to the acid I would add extra because having the acid concentration lowers the rate at the start.
The effect of Temperature
As you increase the temperature, the rate of reaction increases. Approximately, for many reactions happen at room temperature, the rate of reaction doubles for every 10°C rise in temperature. It may be that the rate doubles every 9°C or 11°C or. The number of degrees needed to double the rate will also change gradually as the temperature increases. Increasing the temperature increases reaction rates because of the large increase in the number of high energy collisions. It is only these collisions which result in a reaction.
www.chemguide.co.uk/physical/basicrates/temperature.html
The effects of catalysts
A catalyst is a substance which speeds up a reaction, but is chemically unchanged at the end of the reaction. When the reaction has finished, you would have exactly the same mass of catalyst as you had at the beginning.
http://www.chemguide.co.uk/physical/basicrates/catalyst.html
The effects of surface area
The more finely divided the solid is, the faster the reaction happens. A powdered solid will normally produce a faster reaction than if the same mass is present as a single lump. The powdered solid has a greater surface area than the single lump.
Methods:
Step 1: First my group and I measured out 50.0 CM2 of sodium thiosulphate into a burette, we didn’t need any water for this, so none was measured out. From the burette I poured the sodium thiosulphate into a flask. We placed the flask on top of a piece of paper with an x on it. We put a thermometer in the flask to measure the temperature. The stop watch was then started to time how long it took for the x to disappear, then we repeated it four more times.
Step 2: Secondly, we measured out 40.0 cm2 sodium thiosulphate from the burette and put it into a flask. Into a measuring cylinder we measured out 10cm2 of water. Again I also recorded the temperature of acid and then added the water. I started the stopwatch. And waited till the X disappeared, and then I repeated it three more times.
Step 3: further more after I measured out 30cm2 of sodium thiosulphate from the burette and put it in the flask. From a measuring cylinder 20.0cm2 of water was measured out, when I did this I was recorded the temperature of the acid. After I put the two together and again recorded the results on how long it took for the X to disappear. Then I repeated it two more times.
Step 4: Also, we measured out 20.0cm of sodium thiosulphate from a burette and poured it into flask. While I was keeping track I measuring out 30.0cm2 of water from a measuring cylinder. I then added the water to the acid and again recorded the time it took for the ‘X’ to disappear. Then I repeated it once more.
Step 5: I then did the fifth part of the experiment. Our group measured out 10.0cm2 of sodium thiosulphate by a burette, we then measured the temperature when we put it into the flask, and then put 40.0cm2 of water with it. I did this with a measuring cylinder, and then we recorded the results for the final time.
Results Table:
The results I got were made from me and my classmates by doing the experiment and recording the results.
I got the rate by doing, 1 divided by the average time, times by one hundred. Make the answer to one decimal pace.
I got the average by adding the times up and diving them by how many times there are (3).
Equipment - Accuracy -
50cm3 measuring cylinder 2cm3
10cm3 measuring cylinder 1cm3
Burette 0.05cm3
250m3 measuring cylinder 2cm3
% Error=Accuracy of equipment x 100
Quantity of substance
-We needed a burette to measure all three chemicals.
The degree of accuracy of the burette is very high of 0.05.
Conclusion:
From my graphs I can say that there is a correlation, between the rates of the reaction and concentration of the sodium thiosulphate. I can say this because my graphs and my data support it; also my line on my graphs, gets steeper as the concentration of the sodium thiosulphate increases. My data is shown in my results table.
Evaluation:
Bibliography
- www.chemguide.co.uk/physical/basicrates/temperature.html
- http://www.chemguide.co.uk/physical/basicrates/catalyst.html
- GCSE Additional science (OCR) Oxford, Twenty first science, text book.
