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Rate of Reaction

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Rate of Reaction Introduction I will be investigating the affect temperature has on the rate of a reaction between sodium thiosulphate and hydrochloric acid. The rate of reaction is the speed at which a chemical reaction proceeds. There are many ways to increase the rate of reaction including: an increase in temperature, an increase in the concentration, an increase in the surface area, an increase in pressure and adding a suitable catalyst. I plan to conduct an experiment using the solution of dilute sodium thiosulphate and hydrochloric acid to observe the affect that temperature has on the rate of reaction. Equipment list The following apparatus will be used in the experiment: o Heat proof mat o White tile o Bunsen Burner o Tripod o Gauze o Sodium Thiosulphate o Hydrochloric acid o Distilled water o Measuring cylinders (x3) o Beakers (x3) o Conical flask o Thermometer o White paper with a black cross o Stop clock o Safety goggles o Tongs Diagram Increasing concentration The rate of a reaction can be increased by using solutions of different concentrations. If a solution is more concentrated there are more reactant particles free to react. This makes a reaction more likely. Increasing concentration simply means we are increasing the number of reacting particles in the same volume of liquid. This means the more concentrated a solution is the higher the frequency of collisions allowing more reactions to happen in a short space of time thus increasing the rate. This would work well for my experiment but I lacked the different concentrations of the solutions, otherwise this experiment would have worked well at investigating the rate of a reaction. ...read more.


When a change in conditions, such as temperature, increases the number of particle collisions increase because the higher temperature makes the particles move faster, with more energy. This means there will be an increase in successful collisions, thus an increase in the rate of reaction. At higher temperatures, more particles have enough energy to react successfully, so the frequency of successful collisions is increased, clearly supporting my theory. Based on this evidence, I predict the graph to look somewhat like this, with a rise in temperature affectively doubling the rate: My preliminary work has shown that it is very important to keep everything very accurate; the reactants, temperature and timing are all very important to the outcome of this experiment. It has also informed me of the range of readings of temperatures I will be using; 30, 40, 50, 60 and 70oc. I will do each of these temperatures 3 times for maximum accuracy. Timing will be done in seconds as my reaction to the rate is not fast enough to be done in milliseconds. I also found I would need a way to calculate the rate. The rate of reaction can be measured in seconds-1. This would mean that as the rate increased, the time taken would decrease. Therefore, increasing the temperature would decrease the time. I have also found that when the temperature increased the time in which the reaction took place was lowered. This means the activation energy barrier must have lower for the higher temperatures because at higher temperatures, more particles have enough energy to react, so the frequency of successful collisions is increased. ...read more.


Magnesium + Hydrochloric acid Magnesium Chloride + Hydrogen Mg(s) 2HCl(l) MgCl2(aq) H2(g) Firstly I will set up apparatus as shown in the following diagram: I will then place the magnesium into the hydrochloric acid and seal the conical flask up, so the gas given off (hydrogen) can be collected in the gas syringe. I will conduct this experiment over different temperatures to affect the rate of reaction. I predict that the graph of results will look like this: When the temperature is at 30oc the particles are moving slowly with little energy so the percentage of successful collisions is low. However there are lots of available particles so the rate at the start of the experiment is high compared with the rate at the end of the experiment where most of the particles have now successfully collided and only a few remain to successfully collide with each other and produce hydrogen. This is why the curve gets less steep as time goes on. When the temperature is at 70oc the particles are moving much more quickly with a lot more energy so percentage of successful collisions is very high, making the curve very steep at the start of the experiment meaning the rate is very high. But the rate overall is lowered due to the remaining particles that have yet to successfully collide with each other after randomly meeting. Thus to calculate the rate I must use the time at when all the particles have collided successfully and produced the maximum amount of hydrogen possible. Here is the graph that was produced: Again, as you can observe the rate doubles with temperature, in theory, which backs-up my results from the main experiment. ?? ?? ?? ?? Sam Mulholland Coursework ...read more.

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