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Investigating the reaction between sodium thiosulphate and hydrochloric acid.

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Introduction

Investigating the reaction between sodium thiosulphate and hydrochloric acid Planning In this investigation I must produce a piece of coursework investigating the rates of reaction. The rate of reaction is the loss of a reactant or the rate of formation of a product during a chemical reaction. There is five factors that could effect the rate of a reaction, according to the collision theory of reacting particles: temperature, concentration (of solution), pressure (in gases) surface area and catalysts. The factor that I am going to investigate is temperature. My aim in this investigation is to see the effects of the change of temperature on the rate of reaction. The reaction that will be used is: Sodium Thiosulphate + Hydrochloric Acid Na2S2O3 (aq) + 2HCl (aq) During the experiment temperature will be my variable (thing that I change) while everything else will remain constant. The whole Idea of the experiment is to mix the two solutions together and see how long it takes for a cross, which will be underneath the beaker with the mixture, to disappear. ...read more.

Middle

However if one set of results is entirely different to the other, a third experiment will be performed to replace the anomalous set of results. Safety - A pair of goggles will be worn during the heating part of the experiment in order to protect the eyes. Fair Test - In order for my findings to be valid the experiment must be a fair one. I will use the same standard each time for judging when the X has disappeared. I will make sure that the measuring cylinders for the HCl and thiosulphate will not be mixed up. The amount of HCl will be 5 cm3 each time, and the amount of thiosulphate will be fixed at 15 cm3. Prediction I predict that as the temperature increases the rate of reaction will also increase. This is because as there is a ten degrees rise in temperature the reaction time will half. This means that when I draw my graphs they will both have a positive correlation, and will probably be curved as the increase in the rate of reaction will not be the same as the temperature is increased. ...read more.

Conclusion

Collisions between reacting particles are therefore more likely to occur. My graph shows that the difference of rate between increasing temperatures (excluding the anomaly of 30�C) was increasing in steps of 6-10 (9.17 to 15.37 to 24.28 to 31.67). However, once again there is a giant gap in the last temperature increase - at 60�C the rate of reaction is 31.67 and at 70�C it is 57.03. For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area. (Last paragraph internet source. www.chemguide.co.uk) ...read more.

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