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Rates of reaction.

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CHEMISTRY COURSEWORK RATES OF REACTION Many people are interested to know how to alter the rates of chemical reactions. Fertiliser manufacturers are interested in speeding up the formation of ammonia from nitrogen and hydrogen. Car manufacturers are interested in slowing down the rate at which iron rusts. This shows that rates of reaction is a very important factor within industries today, and in order to demonstrate how a particular factor can alter the speed of a reaction the outcome variable of my investigation to follow is: How a chosen factor affects the rate of reaction of Magnesium and Hydrochloric Acid. Reaching this outcome will consist of choosing a relevant factor with the assist of background knowledge, applying the factor whilst experimenting, measuring the rate of reaction and concluding the outcome. In order to choose a relevant factor I will initially need to observe the different variables: 1. The concentration of a reactant. The higher the concentration, the more molecules per unit volume are available for the chemical reaction, thus more successful collisions occur and reaction rate increases. In regard to my investigation: increasing the concentration of hydrochloric acid molecules would increase the frequency or chance at which they would hit the surface of magnesium in order to dissolve them, which would increase the speed of product formation. 2. The temperature of the reactants. Higher temperature results in particles moving faster, successfully colliding more often and an increase in the reaction rate. For example by increasing the temperature, the magnesium and hydrochloric acid molecules will gain kinetic energy which will cause them to move faster. The increased speed will also increase the chance of collision, hence the rate will increase. 3. The surface area of a reactant. The larger the surface area, the more collisions and the greater the reaction rate. For example smaller pieces of the same mass of magnesium would have a greater surface area compared to larger pieces. ...read more.


15) * Bottle of hydrochloric acid and pipette * 100cm beaker * 100ml measuring cylinder * -5�C -110�C thermometer * Bunsen burner * Heatproof mat * Tripod * Wire Gauze * Splint * Digital Stop Clock * Scissors * Ruler Below is a diagram showing the required set-up of apparatus: The following steps will need to be carried out in order to conduct an accurate and more importantly successful experiment. 1. Begin by setting out the apparatus as shown in the diagram above. i: Ensure the heatproof mat is placed on a clean and flat surface on the desk. ii: Measure 15ml of hydrochloric acid using the measuring cylinder and pour the contents into the beaker ready to be heated. iii: The 2cm strips of magnesium should be measured using the provided ruler and then cut out accordingly using the scissors. 2. Using a splint, safely, ignite the Bunsen burner and adjust the air hole so it is half way open and the flame is blue. 3. Knowing the first range of temperature is 30�C, pay close attention to the �C shown on the thermometer and carefully remove the beaker from the gauze once the required temperature is reached. 4. Put a 2cm strip of magnesium into the beaker and instantly start the stop watch timer. 5. As soon as the magnesium disappears, stop the stop watch, and record the time into your results table. 6. Repeat stages 3-5 again, but stage 3 should be altered so the temperature of the substance is 10�C higher than the one before. i: This procedure should continue until you have recorded all results up to �90 C. 7. Repeat the whole experiment again in order to increase the accuracy of results which will make an average calculation possible for each recording. Safety is a major factor that needs to be kept in mind at all times: * Before the apparatus are setup, it is required safety goggles are worn, the desk is clear of all stationary and books and bags are placed away from the table. ...read more.


Possible improvements: * In order to exclude the scopes of errors mentioned above regarding changing temperature, it would be convenient to conduct reactions in a thermos or similar container which would trap the heat. This would keep the temperature constant and in return increase the accuracy of results. * Even though two repeats for each recording was accurate enough to produce a reliable average, increasing this to three or four recordings would produce a range of results which could then be analysed in more detail. From this possible impediments of restrictions may also arise, which whilst analsying may bring about new theories affecting the reactions. * As mentioned earlier, a more precise time measuring device would be useful instead of a stop watch. This would obviously be to produce better, pr�cised results and one that would possibly exclude the need of manual operation. Extending the investigation: * It would be useful to experiment temperatures below 30�C. This would enable me to observe the reactions and behavior of lower temperatures. And primarily with the last three temperature recordings it was noticeable that the points were closer which explains the flat curve produced at the end of graphs that produced a curve. This would enable me to observe the point at which reactions are unable to exceed; therefore it would be of use to observe temperatures exceeding 90�C. * Another method of measurement would be counting the bubbles formed in a reaction. This would require the need of better equipment, but I believe this would form interesting results. * It would also be interesting to experiment the influences of the other variables, as mentioned at the beginning of my coursework. I was able to briefly experiment concentration in my preliminary work, but it would be interesting to do a continuous specialised experiment and also a new variable that comes to mind: light. SECONDARY SOURCES OF INFORMATION: Internet sources used to construct my background knowledge: * http://www.wpbschoolhouse.btinternet.co.uk/page03/3_31rates.htm * http://www.scool.co.uk/topic_quicklearn.asp?loc=ql&topic_id=11&quicklearn_id=1&subject_id=21&ebt=248&ebn=&ebs=&ebl=&elc=4 * http://www.webchem.net/notes/how_far/kinetics/rate_factors.htm NIKESH PARMAR 11E 1 ...read more.

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