Gcse Chemistry Coursework

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| Chemistry Coursework | How does the concentration of Hydrochloric Acid affect the rate of reaction between Hydrochloric Acid and Sodium Thiosulfate? | | | Initial Planning The aim of my coursework is to investigate the variables that increase the rate of reaction. There are several equations that can be investigated. The main 3 equations are: 1) Hydrochloric Acid + Marble Chips Calcium Chloride + Water +Carbon Dioxide 2HCl (aq) + CaCO3 (s) CaCl2 (aq) + H2O (l) + CO2 (g) 2) Hydrochloric Acid + Magnesium Magnesium Chloride + Hydrogen 2HCl (aq) + Mg (s) MgCl2 (aq) + H2 (g) 3) Hydrochloric Acid + Sodium Thiosulfate Sodium Chloride + Sulfur Dioxide + Sulfur + Water HCl (aq) + Na2S2O3 (aq) NaCl (aq) + SO2 (g) + S (s) + H2O (l) In equation 1, the CO2 produced is monitored over a certain period of time. The more CO2 produced over this time, the higher the rate of reaction. In this equation, there are 3 possible independent variables: a) changing the size of the marble chips (e.g. large, small, powdered) whilst keeping the mass the same, b) changing the mass of the marble chips whilst keeping the size the same (e.g. all powdered), or c) changing the concentration of the hydrochloric acid. In equation 2, the hydrogen is measured by the loss of mass. This is done my placing the reaction on a table top mass balance. There are also 3 independent variables that can be changed in this experiment: a) the mass of magnesium, b) the surface area of the magnesium (the magnesium is in strips and is the same size for all experiments), or c) the volume of hydrochloric acid used. In the final equation (3), the reaction is measured by looking at the yellow precipitate formed by the sulfur. When the reaction is cloudy, the experiment is complete. The independent variables

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