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Investigating The Effect of Concentration On The Rate Of Reaction of Sodium Thiosulphate & Hydrochloric Acid

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Investigating The Effect of Concentration On The Rate Of Reaction of Sodium Thiosulphate & Hydrochloric Acid Problem I am measuring the rate of reaction (how fast a reaction takes place) of sodium thiosulphate and hydrochloric acid when affected by the concentrations being altered. In this coursework I am investigating what effect the change in acid concentration will have on the rate of reaction. According to the 'Collision theory' there are different variables that can be used to change the rate of a reaction including temperature, concentration, catalysts or increasing the surface area of solid particles. Increasing the temperature gives particles more energy, which means they will be moving around faster, and increases the chance of collisions that will break bonds. Increasing concentration increases the likelihood of collisions because there are more particles confined to a space. Using a catalyst provides an alternative reaction mechanism with lower activation energy. Activation energy is the energy needed for reacting particles so that they can collide and break bonds to create new bonds. The aim of the experiment is to see the effects of a change in concentration on the rate of a reaction between sodium thiosulphate and hydrochloric acid. ...read more.


Method: First, I will measure the right amounts of sodium thiosulphate and hydrochloric acid into two separate test tubes. They will then be put into the beaker together. The experiment will be done with the substances at room temperature. This means that the beaker will be filled with Na S O and HCl via two measuring cylinders and placed on the tile marked with a cross. The amount of Na S O and HCl being put in the beaker will be determined by prior tests, but they will only need to be quite small amounts. As soon as the two substances are mixed together, the stopwatch will start timing and it will stop when the cross is obscured. This will act as a visual aid in seeing when a sufficient reaction has taken place. The results will then be written down and recorded. The same will then be done for the next amounts in the series of tests and so on. Each test will be repeated approximately 3 times for the Different amounts so that a better range will be given and an average will be taken and sued for the graphs. ...read more.


I have found that as the concentration is increased the time taken for the reaction to take place decreases. This means the rate of reaction increasers as it takes less time for a reaction to take place, so more take place per second. Graph The graph shows that the difference of rate between increasing temperatures was pretty much regular. However, there is a giant gap in the last concentration increase. For this to fully make sense it is necessary to recap the collision theory briefly: 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. Mike McLoughlin ...read more.

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