Collision theory states - Sample Essay
I have been asked to investigate the effects different factors such as concentration and temperature have on the rate of reaction The rate of reaction is the loss rate of a reactant or the rate of creation of a product during a chemical reaction and it can be measured by dividing one by the time taken for the reaction be completed.
Collision Theory states that an increase in concentration, temperature, surface area and the use of a catalyst in a reaction will either increase the rate of reaction by increasing the rate of collision between reactant particles, increase the success rate of collisions between the reactants or both of these reactions, there is also another factor which effects the rate of reaction, but is only applicable in gasses, that factor being pressure.
I have chosen to investigate the effects of Concentration on rate of reaction, as it is the most accurately achievable while still challenging factor to change. Method: Equipment- 1x conical flask 2x 50ml measuring cylinder 1x 10ml measuring cylinder 1x pipette Sodium Thiosulphate Hydrochloric acid Water Stop clock Safety goggles Plain paper with a black cross on it. Add 10ml of HCL to a conical flask, by All procedures will be undertaken with safety goggles on.
After assembling all of the equipment I will pour as close to 10 ml of hydrochloric acid into the 10 ml measuring cylinder, using the pipette to get the amount as close as reasonably possible, I will when doing this take into account surface tension and hence fill so the actual amount in the measuring cylinder is at 10ml not a little under as it may appear. I will then add (starting with 50ml descending in steps of 5ml to 20ml) sodium thiosulphate to the 50ml measuring cylinder.
Following this I will add (starting with 0ml rising to 30ml in steps of five, in such a manner that the total volume of water combined with sodium thiosulphate Is always at 50ml) water to the second 50ml measuring cylinder. I will then add the two 50ml measuring cylinders contents into the cylinder containing the sodium thiosulphate, leave the cylinder for 10 seconds for the liquids to mix together (after swirling gently 10 times) before emptying the hydrochloric acid into the conical flask, followed by the mixture of sodium thiosulphate and water.
The conical flask will be left on top of the piece of paper for the addition of the latter and when the second liquid is poured into the conical flask the stop clock will be started, I will then proceed to watch the view the black cross on the piece of paper bellow the conical flask until the point I can no longer see the black cross, at which instance I will stop the stop clock and record the time taken on a table along with the volumes of liquids used, I will also take the temperature at the time to make sure if there is any major discrepancy caused by the temperature I will know that this is the case and will be able to identify and explain these results.
I will repeat this for every one of the concentrations three times, and if any results are not reliable enough then I will re do the experiment for these results. Collecting and Interpreting Data I have collected a my results, with three sets of results for each concentration, all initial results at 23 degrees centigrade although due to the outlier present at, along with unreliability, of results at a certain concentration tests had to be redone at this concentration although at a lower temperature of 21 degrees centigrade.
The range of results does seem to be large enough, with three sets appearing to give me a reliable set of results and confirming that the results I do have are close enough. Sodium Thiosulphate (ml) Water (ml) Hydrochloric acid (ml) Time taken for reaction in seconds
Test 1 Test 2 Test 3 Average Above is the graph showing initial results, with the questionable results being the 15ml Water to 35ml Sodium Thiosulphate results. Bellow you will be able to the results with the new results on, the average is also marked on to this to show how close together the results are and the actual table containing these results (both original and re-dos) is also attached.
Since on the lower graph all sets of data are within 5% of each other for time we can assume they are reliable as well as accurate. Sodium Thiosulphate (ml) Water (ml) Hydrochloric acid (ml) Time taken for reaction in seconds Test 1 Test 2 Test 3 Average 5These graphs both show, the second more so, show that as concentration decrease the reaction time increases slowing more and more as the concentration decreases. This can be explained by collision theory, and hence I will so.