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Experiment to Investigate the Rate of Reaction between Hydrochloric Acid and Sodium Thiosulphate, with Varied Concentrations.

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Experiment to Investigate the Rate of Reaction between Hydrochloric Acid and Sodium Thiosulphate, with Varied Concentrations PLAN Introduction: We have been asked to produce a piece of coursework that investigates the rate of reaction between hydrochloric acid and sodium thiosulphate. The rate of reaction is "the rate of loss of a reactant or the rate of formation of a product during a chemical reaction" (essaybank.co.uk). The rate of reaction is measured "by dividing 1 by the time taken for the reaction to occur", (1/time taken). As the hydrochloric acid (HCl) particles are reacting with the sodium thiosulphate (Na2S203) particles they will obviously go through a chemical reaction which will produce an insoluble precipitate. This will be a yellow precipitate of sulphur. The chemical equation for this reaction is: HCl + sodium thiosulphate sodium chloride + sulphur dioxide + sulphur + water. 2HCl (aq) + Na2S2O3 (aq) 2NaCl (aq) + SO2 (g) + S (s) + H2O (l) For any reaction to occur, the collision theory also occurs. This is where the reactant molecules, of the reaction, collide with each other, to form a product. For example in the diagram below, the reactants 'A' and 'B, when they collide with sufficient energy, they produce product 'C'. There are many physical, chemical and biological factors that can affect the rate of a reaction. According to the collision theory of reacting particles there are several factors which affect the rate of a reaction: the temperature, the concentration of the solution, the pressure if the reactant is a gas, the surface area of a reactant if it is a solid, and the catalysts that are involved in the reaction if there are any. A catalyst is "a substance which increases the speed of a reaction, without being changed or used up in the reaction" (Chemistry GCSE Double Science Revision Guide Higher Level- Richard Parsons). Catalysts are very important as they spied up the rate of reactions and this is a major reason why it is used in industries as it save money as reactions can take place at lower temperatures which effectively means lower cost. ...read more.


This is because the hydrochloric acid and the sodium thiosulphate have already been reacting in the previous reaction, which means they will be less concentrated as it has lost some particles during successful collisions in the last reaction. Obviously this would affect the present reaction, as there are now fewer hydrochloric acid particles and sodium thiosulphate particles to react with eachother which would decrease the rate of reaction. The problem with this is that it will make the experiment unfair. The concentration of the hydrochloric acid must be kept constant for each reaction, in the conical flask. This is done because it is a requirement for the experiment, which is to find the how the rate of reaction is affected with varied concentrations of the sodium thiosulphate. Safety: This experiment poses many dangers to the safety and health of others and myself and so I will ensure that the following precautions are followed. * Hydrochloric Acid is corrosive. Avoid contact with the skin. If contact does occur rinse thoroughly with cold water and alert your supervisor immediately. * Hydrochloric acid is used in detergents as toilet cleaner and can therefore be used in bleaching agents. So for extra safety precautions wear a lab coat or some form of protective clothing so it does not bleach of damage your clothes. * Wear goggles when conducting the experiment to avoid any contact of harmful substances with the eyes. Contact of the eyes with hydrochloric acid is dangerous because corneal burns can occur very rapidly. Therefore, safety glasses or, preferably, goggles should always be worn when handling concentrated hydrochloric acid. If, however, any hydrochloric acid does come into contact with the eyes, wash eyes thoroughly with water and alert your supervisor immediately. * Do not leave your experiment unattended as accidents may occur if it is left unsupervised (this would also affect the accuracy of your results if you misconduct the experiment). Results: Results Table 1 (For the first set of results): VOLUME OF HYDROCHLORIC ACID (cm�) ...read more.


This may also be the reason why the results I obtained did not fit exactly into a curve for the graph I constructed, as some of the values were outside the curve. These results are known as anomalous points. To solve this problem, I could repeat the experiment but this time I would use the same hydrochloric acid from the same bottle and the same sodium thiosulphate from the same bottle so it would provide an even more accurate reading, as the concentration of the liquids will be the same. The anomalous points could have been caused by several other reasons such as that the temperature could have fluctuated by an amount high enough to cause the rate of reaction to increase or decrease enough so that it did not follow the normal pattern as the other reactions followed. Also the anomalous points could have been due to a slightly unequal amount of one of the reactants which affect the rate of reaction. Also the experiment could have been jogged which would have stirred the solution around a little which would cause more successful collisions to occur and the rate of reaction to increase. There were a few difficulties that I encountered whilst conducting my experiment. Firstly I found it difficult to get the right volume, as the measurement units were not small enough. I could overcome this by using a pipette, which would allow me to get the volume more precise, or I could use a measuring cylinder with small measurements. Also I found it hard to decide whether the large X had disappeared or not as I was looking at the cross for a long period of time. This can be overcome by using the ultra-violet lamp and photoelectric cell technique. Another difficulty that I faced as starting the stopwatch as soon as all the hydrochloric acid was added to the conical flask. Yannick Ren� 2 1 ...read more.

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