Experiment is to investigate the rate of reaction between hydrochloric acid and calcium carbonate :: GCSE Chemistry Coursework Investigation

Experiment is to investigate the rate of reaction between hydrochloric acid and calcium carbonate Hydrochloric acid + Calcium Carbonate Þ Calcium Chloride + Water + Carbon Dioxide 2HCl (aq) CaCo3 (s) CaCl2(s) H2O (aq) CO2 (g) There are a number of variables in this experiment and these are listed below as input variables and outcome variables. The input variables are the ones that I can change in order to affect the experiment and the outcome variables are the ones I will measure to see how the input variable has affected it. Input Variables --------------- Amount of calcium carbonate Amount of hydrochloric acid Surface area of calcium carbonate Concentration of hydrochloric acid Temperature of hydrochloric acid Introduction of a catalyst Outcome variables ----------------- Amount of calcium chloride released Amount of water released Amount of carbon dioxide released Change in weight Out of these variables I will use concentration as my input variable and amount of carbon dioxide released as my outcome variable. You can see how I will use and measure these variables in the method section of this investigation. My preliminary results can be found in appendix 1. These show what measurements of the input variables I decided to use and why I decided this. Prediction ========== I predict that as the concentration of the hydrochloric acid decreases the rate of reaction will decrease and therefore the time taken for 75ml of gas to be released will increase. The reason I believe this is that chemical reactions occur when particles of the reacting substances collide. Increasing the number of the particles increases the number of collisions per second and this increases the reaction rate. In the reaction between hydrochloric acid and calcium carbonate you can increase the number of particles in two ways. The first of these is to increase the surface area of the calcium carbonate. Although this does not directly increase the number of particles, it does increase the number of particles that are available for the H+ ions to react with. This is shown in diagram 1 of appendix 2. The second way to increase the concentration in my experiment is to increase the concentration of the hydrochloric acid. By doing this you increase the number of H+ ions available to react with the calcium carbonate and therefore the number of collisions per second between the two increase. If the number of collisions per second increases then the reaction rate will increase. This is demonstrated in diagram 2 of appendix 2. In order to gain perfect results I would have to use the following weights of each component of the formula and introduce nothing else into the equation. All of the weights are in grams CaCO3 + 2HCl Þ CaCl2 + H2O + CO2