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Find out the effect of concentration on the reaction between Sodium Thiosulphate and Hydrochloric Acid.

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Rate of Reaction Introduction: The RATE of a reaction is the SPEED at which a reaction happens. If a reaction has a low rate that means the molecules combine at a slower speed than a reaction with a high rate. Some reactions take hundreds, maybe even thousands of years while other can happen in less than one second. The rate of reaction depends on the type of molecules, which are combining. There is another big idea with rates of reaction... COLLISION THEORY. The collision theory says that the more collisions in a system, the more likely combinations of molecules will happen. So if there are a higher number of collisions in a system... More combinations of molecules will occur, the reaction will go faster, and the rate of that reaction will be higher. Forces that change the speed of reactions: Reactions happen, no matter what. Chemicals are always combining or breaking down. Over and over again but not always at the same speed. There are a few things, which really affect the speed of the reaction and the number of collisions that can occur. Temperature Increasing the temperature increases the speed of the reacting particles and faster particles collide more often than slow ones. The increase in the number of collisions leads to an increase in the collision frequency and rate of reaction. Increasing the temperature also gives the particles more energy so that they collide with more violence. Energetic particles have a better chance of their collisions leading to a reaction. ...read more.


rate of reaction using concentration as a factor, so there is a number of things I need to make sure that test is fair. Firstly, I need to keep a chemical at a constant concentration. So, in this experiment I have chose to keep hydrochloric acid at a constant concentration. I could have, however, used sodium thiosulphate as a constant, but I had chosen to use hydrochloric acid. I must make sure that the solution is kept at a constant volume throughout the experiment. If the volume is different, then it could give different results to if it was at a constant volume. I must also make sure that I add both the water and the sodium thiosulphate at exactly the same time (into the conical flask with the hydrochloric acid in it), or it could affect the results of the experiment. I must start the stopwatch at the exact time as hydrochloric acid into the Sodiumthiosulphate and distilled water. Lastly I must ensure that the conical flask is completely clean and free of any water or any other substance before I attempt to start the next experiment. Method: 1. I wore lab coat 2. I collected the apparatus and set up as shown in diagram. 3. On a clean white paper I marked cross (x) 4. Then I put conical flask on the white paper, marked x on it. 5. I wrote Na2S2O3 on one conical flask, HCl on other one to avoid the mix up. ...read more.


This can easily be seen when I look at the results table. My results support the prediction I made because I said 'the greater the concentration of Sodium Thiosulphate the faster the rate of reaction time.' I believe I was correct 'the reaction time will be faster with a more concentrated solution because, the more particles there are, the frequency of successful collisions is greater and therefore the reaction rate is speeded up'. My graph is a smooth curve. I am confident with my results because my line is on nearly all of the points. My graph shows that the more concentrated the thiosulphate solution the quicker the cross disappears. I know this because when there is 45cm� of sodium thiosulphate and no water it only took 15 seconds for the cross to disappear whereas when there is 5cm� of sodium thiosulphate and 40cm� of distilled water it took 224 seconds to disappear. Evaluation: I feel that my experiment was fairly successful, and relatively easy to perform. I had two anomalous results shown in my graph after an average over three measurements. I can say that looking at my results when I repeated results they were quite close together. To improve my results I would do more preliminary work to make sure my method was as accurate as possible and that I was more familiar with doing the experiment. I think it would be a good idea to repeat the experiment more than two times to improve my results. I think it would be better to work with another person so one person will put substances together while the other will start timing. ...read more.

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