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Chemistry - Rates of Reaction.

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Science Coursework; Chemistry Rates of Reaction Aim and background information: The purpose of this study was to investigate the catalysts of reaction rate between substances; the elements used to test this were chips of calcium carbonate (CaCO3) and hydrochloric acid (HCl) of varying molarity. In order to complete the task I first had to examine and comprehend the basic principles that form reaction rates. Primarily, two theories must be studied, these are the Collision theory and the principles of Activation energy. Collision Theory:- The collision theory states that in order for a reaction to occur between two species they must come into contact with each other. They must also collide the right way and with enough energy for the bonds to break (this is known as the Activation energy which is examined below). The more particles that are required to obtain a certain reaction, the less likely the chances are that it will occur. This is mainly because most reactions necessitate a specific collision between two particles (eg. a certain molecule of one species colliding with a certain bond of the other), so the chances of reactions occurring that involve more than two species become very remote. Activation energy:- Even when the particles are orientated so that a reaction can occur this still will not happen unless there is a minimum amount of energy, the Activation energy. ...read more.


fair test and accurate results the following factors must remain constant: * The weight of the calcium carbonate must remain constant or relatively similar, as must the surface area of the CaCO3. * The light intensity of the environment must remain constant, this will be lab conditional, preferably on the same day so the natural light intensity is the same. * The temperature of the substances will be room determined at all times, no species will be heated or cooled. * The removal of all catalysts must be ensured this involves the sanitation of all equipment after each test. * The amount of acid (regardless of molarity) used in the experiments must remain constant. * The time allocated for measurement and the point at which timing commences must remain constant. Notes and information on 'molarity': A molar substance is one with a certain amount of particles in. 1 molar of any substance has the same amount of particles as any other 1 molar solution and so on. A 1 molar solution has 6.3x 1023 particles. The molar principle was devised to give a measurement that could be used to compare against others. If I wanted to make a 1 molar solution of Hydrochloric acid I would place 36ml of the acid into 1 litre of water, because the chemical formula of Hydrochloric acid is HCl, which equates to 35 Cl and 1 H. ...read more.


Having supplies of varying molarities of HCl acid at hand could solve this. * There is obviously a small delay between looking at the stopwatch and reading the burette, this coupled with the possible inaccuracy of the readings themselves increased the margin of error in my experiment. * Contrary to my plan the experiments were carried out over two separate days, this meant a variation in the room temperature and light intensity conditions of the experiment. I would have preferred to complete all the practical elements in one day. As I commented upon in my analysis it would have been beneficial to have textbook values at hand for this experiment as they would aid me a great deal in calculating my margin of error and reliability of the results. Also mentioned in the analysis was the lack of a larger burette, the 2m HCl acid, and to an extent the 1m, released 50cm� of hydrogen far quicker than the 10-minute termination time. To extend upon my investigation I could try the reaction with a more varied array of molarities and at different temperatures. I could then find the optimum temperature for the reactions to take place in. I could also try different acids such as sulphuric (H2SO4) and nitric acid (HNO3); I could then compare the results and ascertain which acid reacts more quickly with the calcium carbonate. Daniel Murphy Science Coursework: Chemistry Daniel Murphy Page no. 1 ...read more.

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