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How does varying the concentration of Hydrochloric acid in reaction with Marble chips affect the rate of Carbon Dioxide being given off?

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Rate of reaction. How does varying the concentration of Hydrochloric acid in reaction with Marble chips affect the rate of Carbon Dioxide being given off? Hypothesis: Chemical kinetics, the study of reaction rates, shows that three conditions must be met at the molecular level if the reaction is to occur: * the molecules must collide * they must be positioned so that the reacting groups are together in a transition state between reactants and products * the collisions must have enough energy to form a transition state and form into products Some reactions need energy to react, others are spontaneous once all reactants are mixed. When a solution of substances doesn't need any energy to react it is said to be unstable, that is due to the substances having enough energy in their molecular collisions to form a transition state (the state in which both chemicals have broken apart either from their old pairs or from it's own bond and are about to form a product by bonding with the other reactant). Other reactions won't react unless they are given some extra energy, when temperature is increased the molecules collide more and at a greater speed, therefore at some point (different for all reactions) the reaction will take place. Aim: To investigate the effect of varying the concentration of Hydrochloric solution on the amount of Carbon Dioxide given off from the reaction (also investigate other possible conditions under which the speed of the reaction changes): Marble is defined as: crystalline compact variety of metamorphosed limestone; therefore we can say that it contains same chemicals in same proportions as limestone, just a different chemical arrangement, which in our case is irrelevant to the equation: CaCO3 + 2HCl(aq) ...read more.


As the temperature of the experiment is increased one should expect the results to appear in the same manner in relation to other measurements carried out under the same temperature as all other measurements. Although as the temperature under which the experiment is carried out is increased the amount of Carbon Dioxide gas given off should increase. This is due to particles of the reactants colliding at greater speed and therefore carrying more energy to break their bonds and form the Transition State in order to form the product. So one can expect the rate of reaction of the experiment to speed up when the concentration of the reactants is increased and speed up further when the temperature under which the reaction is carried out to increase further. Scientific explanation: As we increase the number of particles that react, the number of useful collisions increases; we could therefore say that as the number of useful collisions increases the number of successful collisions increases. As we increase the temperature the collisions have higher energy to break their bonds, therefore the number of useful collisions that don't react decreases (a collision is useful when it collides with it's reactant). Setting up the experiment: 1. The marble chips have been cut previously 9 by 12cm, but as they may have been inaccurate they were further weighed. A mode mass has been selected, then larger chips were further cut in order to weigh the same amount as the mode mass. Smaller chips were thrown away because if they were to have been added to then the surface area of the smaller chips + their addition would dominate the regular chips on the basis of the reacting surface area and the experiment wouldn't be a fair one. ...read more.


* A large number of results were obtained, giving a broader view of the given reaction. * The experiment was carried out by the plan and all the safety procedures with no accidents or misfortunes. * One could have expected in the Overall time graph to have seen the temperatures to level off as more atoms and particles were used up during successful collisions. However, this change in rate of reaction as reaction proceeded was not apparent and the graphs showed straight lines for each temperature when the lines of best fit had been plotted. This is likely to be because of the relatively small amount (100mls) of CO2 collected which did not allow each reactant to be used up and all possible collisions to be completed. * To improve the accuracy of the experiment, instead of leaving the acid for 5 minutes to warm up, what could have been done is the acid could have been warmed up for longer and had been measured to make sure that it is the right temperature before the reaction starts. This is likely to have provided more accurate results. * The temperatures could have been given a wider scale by measuring the reaction in 10?C and also in 80?C. * Having 5 tries instead of 3 could have evened up the average providing more precise data. * Having more time the apparatus could have been changed in order to allow measuring the total amount of Carbon Dioxide gas given off, this would allow us to see the point at which the reaction rate got slower for each temperature. This was not possible due to 100ml measuring cylinders being used, which limited the experiments' potential. By Paul Markov ?? ?? ?? ?? ...read more.

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