Rates of reaction Essay Example for Free

Rates of reaction Essay Refer to: GRAPH 1 The basic trend of the graph shows that time of reaction (y) decreases at a decreasing rate. More specifically the curve of best fit shows that the average temperature (y) is inversely proportional to the average time of reaction (x). This forms an equation of y=mi (1/x) Time of reaction = constant x (1/temperature). As the constant is set as 1, this can be interpreted as y=1/x. In order to validate this I will produce a line graph showing the relationship between the two. The calculations of 1/temperature are also tabulated below. 2 As can be seen from the graph the time of reaction increases at a constant rate which proves that the time of reaction is proportional to 1 over temperature. Although the points do not form a perfect straight line, using the line of best fit it is possible to determine the time taken by any given temperature. For example a 1/temperature of 0. 015 i C would cause the reaction to take approx. 60 seconds. And by dividing 0. 015 by 1, it is possible determine the actual temperature of the reaction. In this case:   1/temperature = 0. 015 1/0. 025 = 66. 66 Therefore temperature = 66i C Hence it would take approx. 60 seconds for a product to be formed when the temperature is 66i C. I have analysed the time of reaction as this was the dependant variable throughout my experiment, but the aim of my experiment is to determine the relationship between temperature and rate of reaction. Therefore I will begin by producing a scatter diagram showing all the recordings. This will allow me to observe the accuracy of results and also, through a visual display, identify any possible recordings that dont follow the usual trend. Using the recordings of time of reaction, it is possible to convert this into a rate using the following formula: 1 / time taken Below are the rates of reaction calculations tabulated and therefore a scatter diagram demonstrating this: The scatter diagram shows positive correlation meaning as the temperature increases, the rate of reaction also tends to increase. In order to distribute the recordings further and more importantly notify a relationship I will tabulate and produce a line graph showing the average time of reaction recordings against increasing temperature. TEMPERATURE (i C) The basic trend of the graph shows that as the temperature increases so does the rate of reaction, which proves my prediction is correct. However as can be seen, the relationship is not linear. The curve of best fit shows that the average rate of reaction (y) is directly proportional to the square root of temperature (x). I have calculated this below and in order to test a relationship I have produced a line graph: The graph shows that the average rate of reaction increases at a constant rate, excluding the second point, which proves that rate of reaction, is directly proportional to the square root of temperature. Using the line of best fit it is possible to find the rate of reaction by choosing any temperature on the graph. For example a Vtemperature of 3i C would cause the reaction to take approx. 0. 00565 seconds. And by squaring the VtemperaturAs the temperature increases the time of reaction decreases.   As the temperature increases the rate of reaction also increases which validates my prediction is correct. And from demonstrating these findings on line graphs, I was able to determine and prove that:   Time of reaction is proportional to 1/temperature and   rate of reaction is proportional to the square root of temperature. EVALUATION: Accuracy: As can be seen from the circled point on the majority of graphs produced from the results taken, this is identified as an anomaly as it disperses away from the usual trend of the graph. There are many reasons to indicate why an anomaly is present; this consists of human errors and equipment restrictions and possible unruly scientific theories that affect the whole experiment.   The method of using a stop watch to measure the time of reaction was not as reliable as to using more precise recording apparatus such as a time measuring and indicating device for example. This is 1) due to the unit of time where all recordings were automatically rounded to 2d. p. and 2) the mature condition of the stop watch used at times caused a lockage in the start and stop buttons, in a case where the time distinction of getting the stop watch to start and stop may have affected the accuracy of a recording.   Furthermore it was impossible to observe and acknowledge exactly when a reaction had been completed; hence product formation. Extra attention was paid to the reaction, however the stop watch timer was only stopped when I believed the reaction was complete. This is unreliable and has no form of justification as this was determined solely through manual procedure.   Again another profound error may have been the amount of hydrochloric acid. I ensured as much solution as possible was poured into the required beaker after being measured in the measuring cylinder, however there were always small drips of liquid that were inevitable. It is illegible whether this has an influential affect; however this regardless opposes the accuracy of the recordings. The temperature of the solution may have not been as intended at the start of the reaction (when the magnesium was put in). This is primarily due to that the beaker was removed from the heat once the thermometer hit the intended temperature, however the distinction in time of removing the beaker from the heating setup area to the flat desk and entering the magnesium may have caused the temperature to fall (significant/insignificantly is unknown). This is due to the reaction being exothermic, transfer of heat to surroundings, which would have caused dramatic changes in temperature throughout the experiment. There are also reasons to compliment the accuracy of my results:   Each recording was repeated twice. This enabled me to calculate an average and gave me the advantage of being able to produce a better analysis overall.   I was able to identify early on during the preliminary work that the magnesium strips may have not been the same consistent size throughout, but during the actual experiment I took extra care in measuring, cutting and comparing the strips to the required identical length. Reliability: In addition to the scopes of errors mentioned above, there are many other incontrollable factors that may have had a form of influence or obstruction. However no significant problems or difficulties were encountered whilst conducting the experiment. My results and conclusion were accurate and reliable enough to verify a relationship that as the temperature increases, the rate of reaction also increases, hence agreeing with my set prediction. I was also able to determine that an increase in temperature, decreases the time of reaction, furthermore the time of reaction is proportional to 1/temperature and the rate of reaction is proportional to the square root of temperature. Improvements: No matter how accurate produced results are, due to the restriction in apparatus provided and the time to complete the investigation, improvements will always be applicable. 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, pri cised results and one that would possibly exclude the need of manual operation. Extending the investigation:   It would be useful to experiment temperatures below 30i 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 90i. 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=qltopic_id=11quicklearn_id=1subject_id=21ebt=248ebn=ebs=ebl=elc=4   http://www. webchem. net/notes/how_far/kinetics/rate_factors. htm.