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sodium thiosulphate

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Investigation: How does the concentration of the acid affect the rate of reaction? The aim of this investigation is to test how concentration affects the rate of reaction. My prediction for my investigation is that the higher the concentration, the faster the reaction will be. My reason behind my prediction is: * The higher the concentration, the more particles there are which will collide with enough energy to overcome activation energy, which is explained as the collision theory. Collision theory explains how chemical reactions occur and why rates of reaction differ. For a reaction to occur, particles must collide. If the collision causes a chemical change it is referred to as a fruitful collision. For a reaction to occur, the reactant particles must collide. Only a certain fraction of the total collisions cause chemical change; these are called successful collisions. The successful collisions have activation energy at the moment of impact to break existing bonds and form new bonds, resulting in the products of the reaction. Increasing the concentration of the reactants and raising the temperature bring about more collisions and therefore more successful collisions, increasing the rate of reaction. When a catalyst undergoes collision with the reactant molecules, less energy is required for the chemical change to take place, and hence more collisions have sufficient energy for reaction to occur, therefore the reaction rate increases. ...read more.


The materials and equipment that I will need for my experiment consist of: * 10g of Calcium Carbonate pieces, which will be used over the course of 5 separate experiments, using 2g in each experiment to with different Molarity. * 0.5M, 0.75M, 1.0M, 1.5M and 2.0M of Hydrochloric Acid (HCl) to test the rate of reaction. * A Conical flask that will hold the acid and Calcium Carbonate whilst the Carbon dioxide is collected and the experiment is in progress. * A gas syringe to collect 40cm3 of the Carbon dioxide and it will give me greater accuracy. * A timer/stopwatch to record the time taken to collect the 40cm3 of gas. * A clamp to hold the gas syringe in place. * A clamp stand to hold the gas syringe and the clamp in place. * A measuring cylinder to measure out the 30cm3 of HCl for each experiment and each Molarity. My method for this experiment is: 1. Set up the apparatus using all the equipment stated above. 2. Weigh out the 2g of Calcium Carbonate using electronic scales to achieve precision. 3. Measure out 30cm3 of 0.5M of HCl for the first experiment using the measuring cylinder. 4. Pour the measured HCl into the conical flask containing the Calcium Carbonate pieces. ...read more.


In my first test there was an anomalous result that was tested again and found that there was a problem with the recording of the data. There can be errors when an investigation like this is taking place and a sample of these errors are stated below: * There may have been a human error of timing, which therefore may give an unfair result because of the precision of the timing or the time taken to stop the stopwatch. * The precision of the equipment may not be to a high standard, which in turn, can give false results or an untrue result. * The concentration may not be correct and the concentration that was used was not the Molarity that was stated on the label or as mixed with the water. * Gas lost from the conical flask when stopper is placed, releasing gas means a longer period of time for the gas syringe to fill up with the Co2. * Different surface areas of the Calcium Carbonate pieces could also affect the final results as, the larger the surface, the faster or slower it takes for the Calcium carbonate to react. If I were to do the investigation again, I would choose different concentrations variables or different weight variables of the Calcium carbonate. Another change that I could make could be the measure of the volume of gas given off at different intervals. ...read more.

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