Rates of reaction between Magnesium and HCl.
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Chemistry coursework: Investigate one factor which affects the rate of reaction of magnesium and hydrochloric acid Plan I am going to investigate how the change in concentration will affect the rate of reaction, between magnesium and hydrochloric acid (HCL). To broaden my investigation I will use a wide range of concentrations in order to evaluate the differences. To ensure that my experiment will be carried out safely, everyone involved in the experiment will wear safety goggles at all stages of the experiment, as hydrochloric acid is a corrosive substance, and protective clothing must be worn at all time whilst conducting the investigation. The practical will be carried out in plenty of space, clear of bags and coats. It is also imperative to consider the safety of other pupils that may be close to the practical. Therefore no one who is not involved in the practical shall be allowed in close vicinity of the experiment. Also care will be taken when handling the equipment and the hydrochloric acid, in order to avoid spillages. Avoid skin contact with hydrochloric acid. Wear goggles at all times. Rinse skin thoroughly if contact is made. Hydrogen gas is flammable. Keep magnesium away from ignition sources such as open flames. Wear eye protection; wash acid spills immediately. In this investigation the dependent variable(s) is the amount of hydrogen produced and the time taken, as this is unknown or controlled prior to the experiment. The independent variables in this experiment will be the concentration used, the amount of hydrochloric acid and water used, the temperature, the length of magnesium of magnesium ribbon, as these are controlled prior to the experiment. Accuracy of the measurement will be the hardest factor to keep constant because it is almost impossible to get completely accurate results in an experiment like this with the equipment we are provided with. Human experimental error is a problem because factors like reaction times, eyesight and our own judgement cannot be changed and the do affect the end result considerably.
Then take the average. The variable that I am going to change is concentration. I predict that the order of the fastest reaction to the least would be from the greatest concentration of 1M to the least concentration of 0.1M. The scientific reason behind my hypothesis is that when increasing the concentration of the hydrochloric acid, the numbers of particles present also increase and so increase the chance of collision. There would be more chance of the particles interacting, and so the reaction will proceed at a faster rate. Analysis From the results that I collected it is clear that the concentration with the fastest rate of reaction was that of 1M hydrochloric acid. The slowest reaction was when the concentration was 01.M. Here is the order of the fastest to slowest reaction: Fastest 1.0M 0.9M 0.8M 0.7M 0.6M 0.5M 0.4M 0.3M 0.2M Slowest 0.1M As shown in the results tables, I collected a first set of results, then a second and then averaged the results in order to obtain fairly accurate and reliable result. I was aiming to do collect a third setoff results but due to the amount of time that was available this could not be completed. My prediction that the highest concentration, 1M, would be the fastest reaction was correct, with a total amount of 22.7cm³ of hydrogen produced. The reaction was extremely fast during the first 30 seconds, however towards the end of that experiment the amount of hydrogen produced stayed the same, as he 20mm strip of magnesium was used up, and therefore no further reaction could occur. The reason why the highest concentration was the fastest reaction is because when increasing the concentration of the hydrochloric acid, the number of particles present also increases and so increases the chance of collision. There would be more chance of the particles interacting, and so the reaction will proceed at a faster rate.
This was especially so for the highest concentration in my investigation of 1M. This did not occur in the low concentration, as the magnesium was slowly reacting with the low concentration acid, and the hydrogen produced was steadily increasing. If I were to repeat this experiment again I would certainly ensure that I would use a substance such as Vaseline to limit the amount of hydrogen escaping. I would also use a more accurate burette, than with 0.01cm³ increments, rather than 0.1, as this would enable me to obtain more accurate results, as the results were fairly close together. As well as this I would ensure than more test were done, for example five as oppose to only two. This would then give me more accurate and reliable results. I could take this experiment further by using a different metal such as Zinc and aluminium. I could investigate other different factors that affect the rate of reaction such as temperature or surface area. I could use a fixed amount of hydrochloric acid, and could alter the surface area of the magnesium strip. I could also use the other method of measuring the rate of reaction. Measure the rate at which the chemicals disappear, rather than measuring the rate of products formed. However, this may be an unreliable method, with the equipment available, at this would be based on ones own judgement. A more advanced and technological way, could be to use a particular program that will enable me to collect data that will instantly be put onto graph, and will show how changing the concentration affects the reaction rate throughout the investigation. The investigation could also be extended to investigate other factors affecting the rate of reaction such as catalysts, temperature of the acid or particle size of the magnesium. Such ideas could give more evidence, or extend my investigation in this subject field. ?? ?? ?? ?? Tarik Saif 11Sn
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