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An Investigation to find out if when sodium thiosulphate and hydrochloric acid react will the concentration of these two substances effect the rate of reaction.

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An Investigation to find out if when sodium thiosulphate and hydrochloric acid react will the concentration of these two substances effect the rate of reaction. Introduction I am going to study the effect of concentration, on rate. In the reaction between sodium thiosulphate and hydrochloric acid. Sodium + Hydrochloric -> Sulphar + Water + Sulphar + Sodium Thiosulphate Acid Dioxide Chloride Na2S2O2 + 2H� -> S + H2O + SO2 + 2NaCl Scientific Background S2O3�� + 2H� -> H2O + SO2 + S Thiosulphate Hydrogen Ion Ion When you increase the concentration of sodium thiosulphate you get more thiosulphate ions. More thiosulphate ions will give more collisions with hydrogen ions and a faster rate of reaction will occur. Solute - solid Solvent - liquid Concentration - molars (M) If you increase concentration then you'll get more ions, making more collisions which will give you a faster reaction. Key Factors The key factors in this experiment are the variables which are: * Room temperature * Concentration of hydrochloric acid * Volume of hydrochloric acid * Concentration of sodium thiosulphate * Volume of sodium thiosulphate Fair Test To make the experiment a fair test, I will change the concentration of sodium thiosulphate. I will keep the volume of sodium thiosulphate, the room temperature, and the concentration of hydrochloric acid all the same. ...read more.


Hydrochloric acid is an irritant, if it is spilled, then it should be flooded with water. Sulphar dioxide is toxic, so all windows and doors should be open, so as to ventilate the room. Although only a small amount is made. Results Concentration of Sodium Thiosulphate (M) Time 1s Time 2s Average Time (s) Rate (S��) Rate (10��S��) % Error 0.20 36 37 37 0.0274 27.4 3 0.16 43 43 43 0.0233 23.3 0 0.12 63 63 63 0.0159 15.9 0 0.08 112 122 117 0.0085 8.5 9 0.04 204 206 205 0.0049 4.9 1 0.08 112 114 113 0.0088 8.8 2 When I used the concentration of 0.08M I found that my results (shown in red) were not accurate enough, so I repeated them (shown in green). Conclusion I can see by looking at my graph that there is a straight line, which tells me that the rate is directly proportional to the concentration. As the graph goes through the origin it shows that when the concentration is zero, then the reaction will not take place, so the rate will be zero as well. Scientific Background The reaction that we are looking at can be shown as an ionic equation, as shown below: S2O3�� + 2H� -> H2O + SO2 + S Thiosulphate Hydrogen Ion Ion When the concentration of sodium thiosulphate is increased then you get more thiosulphate ions. ...read more.


I then repeated it and found the second time was 114seconds, so I discarded 122seconds for the second time, as it was an anomaly. This was probably an error on my behalf as I might have added the wrong volume. Have I Generated Enough Results To Support My Conclusion? Yes, I have generated enough results to support my conclusion. As I used 0 to 0.2M for concentration. This gave me a wide variety of points, so I had a good graph. I also used six different concentrations including zero which gave me enough points, to identify a straight line. Improvements To improve the experiment I could: 1) Add more concentrations, which will give me more points on the graph and it will make it easier to identify a trend. 2) I could use more repeats as this will improve the reliability and will address the problem of the subjective end-point. 3) Also, it is possible that the temperature might vary during the experiment. If I did the experiment in a water bath, it would control the temperature. 4) During the experiment the total time for the reaction to finish is measured, which only gives a measure of the average rate for the whole reaction. It would be better to measure the rate at the start. To do this I would use a P.C. connected to a light sensor and a light. This will also stop the problem of the subjective end point. This document was downloaded from Coursework.Info - The UK's Coursework Database ...read more.

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