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Reaction between Hydrochloric Acid and Sodium Thiosulphate.

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Reaction between Hydrochloric Acid and Sodium Thiosulphate Introduction I will be conducting two experiments to determine how two factors affect the rate of reaction in the reaction between hydrochloric acid and sodium thiosulphate. It is a precipitation experiment. The equation allows us to see how this experiment will help us find how rate of reaction changes Sodium thiosulphate + Hydrochloric acid ---- Sodium chloride + Sulphur + Sulphur dioxide + Water Na2S2O3 (aq) + 2HCl(aq) ---- 2NaCl(aq) + S(s) + SO2(g) + H2O(l) The main factors that affect the rate of reaction of any experiment are -Pressure. By reducing the volume in which the same amount of particles exists the pressure is increased. Once the same number of particles is in a smaller area there is less space in which to move and so the particles are more likely to collide each other. Using a catalyst is another method I could use. A catalyst is a substance, which lowers the activation energy of a reaction without being chemically altered. Energy. By giving the particles extra energy, as heat, they will move faster. This means that they cover more ground and are therefore more likely to collide with each other which in turn makes the reaction faster. (We have to take into consideration the face that not all collisions are successful as they may not react with the amount of energy required (activation energy)). The best way to give energy to a reaction is heat. Concentration. Just as increasing the pressure will increase the number of particles colliding, so will the concentration. By putting more particles into the reaction, the chance that they collide is increased, thus increasing the rate of reaction. Surface area. Particles can only collide when the two sorts can meet. Therefore a reaction can only occur on the surface of a material. Therefore by increasing the surface area (e.g. cutting the substances) ...read more.


The sodium thiosulphate will not be spilled either, as it is dangerous. When the temperature experiment is undertaken, I will wear some rubber protectors so that I do not burn myself. I will stand up so if the beaker was to fall I will be able to move out of the way. Stools will be kept under tables to stop people from falling over. In my results I will put the rate of reaction. This was measured by dividing time by 1. Conclusion Looking at my results I can see that they follow trends that will allow me to ascertain whether my prediction follows or not. The concentration graph gave me a very nice best-fit line, which allowed me to prove that as concentration doubles, rate of reaction doubles (see lines on graph). This fits in with my prediction, so backing it and also fits in with my theories. The Collision Theory works best in this, as there are more particles per square unit, meaning a greater chance of a collision, but also a greater chance of a successful collisions as there is double the amount of particles. At a low concentration, 2.5 cm�, the graph shows that there is barely a rate of reaction, but my results increase at a steady concentration, allowing me to draw an almost proportional best-fit line. At a concentration of 40 cm�, we see that the best-fit line is starting to level off. This means that the acid is becoming too saturated; there are too many sodium thiosulphate molecules in ratio to the hydrochloric particles. This means that the hydrochloric particles will all have reacted, but not all of the sodium thiosulphate particles will have reacted, leaving a surplus. The Collision Theory or Kinetic Theory can do nothing to cause the rate of reaction to increase. From my graph, I can see that at 40 cm�, there were the most amounts of collisions, but at 2.5 cm�, there were so few particles of sodium thiosulphate, there was a lower chance of a collision between the molecules. ...read more.


This gave me the range, which ranged from extremely low concentrations to high enough showing how the rate is affected by the concentration after a certain amount. Also the temperature allowed me to come up with valid results from my graph. My trends allowed me to see that a high concentration will have no affect on the rate of reaction, but a high temperature will increase it. If I had more time I would see if I used a burette and other accurate measuring devices, how they differed from my results. I could also do three results to attain an accurate rate of reaction. I would also extend the temperature to see how slow the rate is at a very low temperature and how extremely high temperature affects the particles and if they will react differently. If I extended this experiment I would see how other factors affect the rate. I would see how catalysts affect it, increasing pressure and increasing surface area. This would be done by either putting the gasses into smaller spaces or cutting the solids into smaller pieces. I would to different sizes to see if a very small piece of substance would have an differing result from a piece of substance slightly larger. Also I could see if the rate of reaction differs between states, solids, liquids and gases. I could test the situation it is in, if gravity has any effect on it, or if a high amount of pressure, like under the sea. This experiment helped me to learn a lot about rate of reactions and the factors. It also helped me to understand how to improve the method, as it was not entirely accurate. It is important to learn about rates of reaction as they come into everyday life. They can allow rusting to occur at a faster rate, but they also help in making chemicals like in plastics, medicines and explosives. Also catalysts are used to crack kerosene into octane and ethanol so there is a higher percentage of gasoline for companies, from crude oil. 1 Ambareen Naqvi 11K ...read more.

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