The effect of temperature on a rate of reaction

I conclude that the higher the temperature the faster the reaction takes place as temp is a factor that affects collision of particles. The higher the temp. the faster the particles move around resulting in more collisions between them. Also the higher the temp the more energetic and effective the collisions meaning that there are collisions where the particles contain enough energy to break existing covalent bonds.

When these existing bonds within reactant particles break they form free atoms that can re-bond and form new products

e.g. with H and Cl .

At a low temp only a few particles have sufficient energy to react on collision. As the temp increases, however the amount of particles with adequate energy to react increase, increasing the frequency of collision and the rate of reaction.

Evaluation

In my expt. the solution of Sodium Thiosulphate reacted with HCl to produce a pale yellow p.p.t of Sulphur which obscured the cross and made it possible for me to record when the they had stopped reacting and the expt was over.

Sources of Error

There were a number of different areas where errors occurred which can explain my anomalous results.

* As the expt progressed I had to rely on the naked eye to determine whether the cross had disappeared or not, which is not an accurate method of collecting information.

* When starting the stopwatch at the beginning and stopping it at the end, time is lost as it is impossible to both start the stopwatch and prepare the beginning of the expt at the same time single-handedly. This causes the recorded time measurements to be unreliable.

* When recording the temp. of the Sodium Thiosulphate in preparation for the expt. I again had to rely on the naked eye to record the temp. of the thermometer. Also after removing the solution from the Bunsen burner the temp. tended to fluctuate up and down, resulting in the recorded temp. often not being the temp. at which the expt took place.

* When the solution was poured and measured, it was often not done accurately meaning some solution was lost, so the amount used was not equal to the amount recorded.

* Unavailability of enough conical flasks and not rinsing the flask properly after each expt. resulted in deposits contaminating the later expts.

* When the two reactants were mixed together in the conical flask by a swirling motion, I could not efficiently record if they were swirled to the same extent every time, meaning some solutions were more mixed than others.

Improvements

* By using electronic instruments that measure both time, light and temp, we would'nt have to rely on the naked eye as we would have exact measurements. We could use a data-logging system, involving a light sensor and computer connection, meaning that results are electronically processed and graphs plotted from the information.

* By using a wider range of readings making the expt more accurate e.g. using a gap of 5°c between the different temp. used rather than a gap of 10°c. As we could have more varied results, which is good for picking the best results as you have lots of choice.

* We could decide the end of the reaction more accuratly if we used a colourimeter which measures the intensity of light being transmitted through the mixture.

* By keeping every aspect of performing the expt such as pouring, measuring and swirling constant, we could reduce room for error.

* By waiting a while before starting the expt to let the Sodium Thiosulphate's temp settle, to ensure that the figure taken down in the temp during the expt.

Limitations

* After a temp rise of 70° it became impossible to record the time taken for the cross to disappear as the reaction took place too quickly. This prevented me from getting a wider range of results.

* By only testing temp with a difference of 10° we limited ourselves as we didn't get many readings which would give more accurate results. So if i repeated the expt I would make sure to have more readings to improve my results.

All in all my results were very accurate with only two anomalous results that can be explained by my sources of error. I still have enough accurate results to form a perfect curve and draw a conclusion from. If I repeated this expt I would take all of the observations I have made from my first expt and make sure that i improved on them, removing room for error and to perfect my results.

Extensions

I could extend this investigation by performing this expt using my improvements from this expt with different chemical reagents, still keeping all other factors except for temp constant. Some different expts I

could use are:

2HCl + Mg Mg Cl + H

2HCl + CaCO CaCl + CO + H O

(The temp is altered at constant intervals in both cases)

After performing one of the expts with Hydrochloric acid and marble chips these results were collected: