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# Rates of Reaction

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Introduction

Rates of Reaction. Sodium Thiosulphate + Hydrochloric Acid Sulphur + Sulphur dioxide + Sodium chloride + Water Results: Temperature (Celsius) Time (in Seconds) 1st exp. 2nd exp. Average Rate (S-1) 21 180 200 190 5.3x10-3 32 135 125 130 7.7x10-3 41 46 48 49 20x10-3 50 31 33 32 31.25x10-3 60 26 24 25 40x10-3 72 12 11 1.5 86.9x10-3 83 5 7 6 166.6x10-3 Conclusion: The higher the temperature, the faster the reaction takes place; the quicker the rate of reaction. As the temperature increase 10 0C the time taken for the sodium thiosulphate and hydrochloric acid to react will half. This can be seen looking at the red lines of interpretation one the first graph. Looking at the second graph we can see that for every 10 0C increase the reaction rate doubles. Had I made a prediction for this experiment I would have probably anticipated that when you double the temperature the reaction rate halves, as I can see from looking at my graphs this does not happen. The reason the rate of reaction does not half when you double the temperature can be explained by collision theory. To explain the collision theory you first have to understand what causes any reaction to start. ...read more.

Middle

If the energy possessed by the two molecules equals or exceeds the minimum activation energy, when the two reactants collide then a reaction will occur. The variation of temperature does not change the activation energy of reaction however increasing the temperature of a reaction does increase the average energy possessed by the molecules. Therefore I can collude that at higher temperatures a greater percentage of colliding molecules will possess the activation energy needed to react and therefore give the impression that more reactions are occurring as I first thought. Evaluation: I do not think my results are very accurate, because my method was not very good and had to rely on human judgement too much. There are several things we did during the experiment, which could have led to inaccurate results. 1. If the thermometer were touching the side of the glass at any time, the temperature would have been hotter than the actual temperature of the sodium thiosulphate. 2. If the thermometer was left in different parts of the beaker for each temperature (nearer/further away from the flame) it may have given inaccurate readings. 3. The thermometers take several seconds at least to register and changes in temperature, therefore when the thermometer said 50oC the actual liquid temperature would have been closer to 55-60 0C. ...read more.

Conclusion

I would thoroughly wash out equipment and if possible use a different beaker for each of the different temperatures. To extend this investigation I would use different chemicals, which react with acid. For example CaCo3 + 2HCl Co2 + CaCl + H2O or Mg + 2HCl H2 + MgCl2 I would use a method to find out whether a rise in temperature increases the rate of reaction. I would compare the results from the tests above with the sodium thiosolthate reaction and observe the temperature increase in the two new experiments and whether they behaved in a similar way to sodium thiosolphate, rate of the reactions doubling for every 10 0C rise in temperature, which was true for sodium thiosulphate and hydrochloric acid. It may also be interesting to make a comparison between the different reaction times depending on the temperatures of sodium thiosulphate and keeping the temperature constant but adding different concentrations of acid. I would draw graphs, for time against P.H and rate against P.H. of the acid. I would try to notice any patterns between the temperate and rate graphs and the P.H. levels and rate graphs, trying to see whether temperature or the concentration of acid has the greater effect on the speed of this reaction. ?? ?? ?? ?? 1 ...read more.

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