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Sodium Thiosulphate + Hydrochloric Acid Investigation.

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Sodium Thiosulphate + Hydrochloric Acid Investigation Plan I must produce a piece of coursework investigating the rates of reaction, and the effect different changes have on them. The rate of reaction is the rate of loss of a reactant or the rate of formation of a product during a chemical reaction. It is measured by dividing 1 by the time taken for the reaction to take place (Rate=1/T). There are five factors which affect the rate of a reaction, according to the collision theory of reacting they are: * Particles * temperature, * concentration * pressure * surface area I have chosen to investigate the concentration have on a reaction. This is because it is the most practical to investigate it would take longer to prepare a solid in powdered and unpowdered form to investigate the particles, and it is difficult to get accurate readings due to the inevitabilities of human errors, and as gas is mostly colourless it is difficult to gauge a reaction changing the presure, if a substance is added to give the gas colour, it may influence the outcome of the experiment. I have desided not to investigate temperature as l have limited time to perform the experiment Aim To see the effects of a change in concentration on the rate of a reaction. ...read more.


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 experiment in order to protect the eyes against any chemicals that may splash. An apron will also be worn to protect the skin and clothing for the chemicals. A gauze and heatproof mat will be used while heating to avoid any damage to the equipment. 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. These precautions will make my final results more reliable and keep anomalies at a minimum so thus make the entire investigation more successful. Prediction I predict that as the concentration of the sodium thiosulphate increases the rate of reaction will increase. This means that the graphs drawn up in my analysis will have positive correlation, and will probably be curved as the increase in rate of reaction will not be exactly the same as the concentration is increased. This can be justified by relating to the collision theory. ...read more.


This means the rate of reaction increasers as it takes less time for a reaction to take place, so more take place. When solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. The graph for concentration shows that when the concentrations were relatively low (10, 15, 20 g/dm3), the increase of rate was also fairly small (increasing from 4.47 to 6.71 to 9.47). There was then a gradual increase in the difference, and between 30 and 35 g the rate more than doubled from 17.90 to 37.56s-1. This shows that there are far more collisions at a concentration of 35 g than at 30 g. 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. ...read more.

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