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For my experiment I am finding out the effects on the reaction rate when magnesium is put into different concentrations of hydrochloric acid.

Extracts from this document...

Introduction

Chemistry coursework: Rate of reaction Introduction My investigation is about reaction rates and finding out what affects them and the correlation between reaction rates and the factors which affect them. Therefore in my experimentation I tried to find out the effects of concentration (the amount of a specific substance in a certain volume of space) on reaction rate. Rate of reaction is the rate or speed at which the chemical reaction (a reaction that changes one set of chemicals to another) takes place. For my experiment I am finding out the effects on the reaction rate when magnesium is put into different concentrations of hydrochloric acid. 2HCL (aq) + Mg (s) MgCl2 (aq) + H2 (g) Hydrochloric acid (HCl) Hydrochloric acid, also known as spirits of salt or muriatic acid is a solution of chlorine and hydrogen. It is a highly corrosive, strong mineral acid which has many uses in industries. It is a clear liquid so if it gets on your skin you will not notice it which means that it would start burning your skin and could get onto food as well. Therefore always wash your hands after handling hydrochloric acid. Collision theory Collision theory is simply understood as the higher the concentration of the reactants, the higher the reaction rate. The more reactants there are the more successful collisions there will be. This theory explains how chemical reactions take place and why reaction rates are different for different experiments. There are many factors which affect the rate of reaction and if not controlled (or kept the same) they can produce varied, unreliable results. The factors that affect my experiment Affecting factors: * Temperature * Concentration of hydrochloric acid * Surface area * Catalysts * Cross contamination When the temperature increases, the reactants gain more energy therefore they are able to move around faster. This means that not only will the reactants collide more often but they will collide with a much larger force. ...read more.

Middle

The averages were attained by finding the mean of three trials. The ionic bonds (a type of chemical bond formed through electrostatic attraction between two oppositely charged ions, H+ and Cl-) between the chlorine and hydrogen are quite strong and when the hydrochloric acid collide with the magnesium strip the bonds between the hydrogen and chlorine break up and the chlorine ion bonds with the magnesium producing magnesium chloride and the hydrogen gas is given off. Mg (s) + 2HCl (aq) = MgCl2 (aq) + H2 (g) In the graph of the hundred percent concentration (50ml) of hydrochloric acid, it is clear that between ten and twenty seconds there is a dramatic increase in the volume of hydrogen produced and this is due to the high concentrations of hydrochloric acid means that there are more collisions and therefore more successful collisions. In a successful collision the hydrogen and chlorine from the hydrochloric acid break apart and the chlorine forms new bonds with the magnesium, the hydrogen is given of as a gas, this is shown in the equation above. This means that if there are more collisions then there will be more reactions which means that more hydrogen gas will be given off . The graph also seems to curve from twenty seconds to thirty seconds. This means that the reaction is nearly over and that most of the magnesium strip has been used up, there is also less hydrochloric acid at this time as some of the hydrochloric acid molecules have reacted with the magnesium. The reaction took forty seconds to finish and this is because there is not any hydrogen being produced and in the graph this is represented by a flat line. The graph of the eighty percent concentration (40ml HCl 10ml water) of hydrochloric acid shows a similar trend to the graph for the hundred percent concentrations. The graph rapidly climbs in the first ten seconds due to the high concentrations of hydrochloric acid and then starts to curve as the reaction is near the end. ...read more.

Conclusion

The results at 80seconds for the 40% and 60% concentration do not follow the general trend of the other results, which is hat as the concentration increases the volume of hydrogen produced also increases. Here the 60% concentration produces on average 25.7 cm3 of hydrogen whereas the 40% concentration produces 26.2 cm3 of hydrogen. This challenges the reliability of my conclusion because it goes against it but it could just be an error because of the length of magnesium strip put in being too long for the 40% concentration which increases the surface area and therefore there will be more collisions. It could also be because of impurities in the magnesium strip for the 60% concentration which also reacts with hydrochloric acid and reduces the surface area of the magnesium and uses up some of the hydrochloric acid by reacting with it. This would decrease the volume of hydrogen gas produced. It could be both of those factors together that caused this effect. I could be more confident in my conclusion if I had other concentrations to work with and enough time to do all these concentrations. Then I could show that the conclusion applies for most concentrations and it would make my conclusion more reliable. I would also continue with the experiments that I have been doing and not stopped at 80 seconds so that I can see more results and see if this is true throughout the whole experiment and show that my conclusion is true and reliable because even when carrying on with the experiment it follows the same trend. I would also check the pH of the water added to make sure that the water added does not alter it in any way and also keep a record of the Ph of the solutions and compare it against what the actual pH should be for that particular concentration and comment on whether it was at the right pH or whether the pH is slightly higher or lower than it should be. ?? ?? ?? ?? ...read more.

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Here's what a teacher thought of this essay

3 star(s)

The preliminary experiment was a very poor experiment, with lots of inaccuracies and reasons to questions its reliability. However, the second experiment was much improved and gave usable results that a conclusion could be drawn from.
Based on the final experiment this is a 3* piece of GCSE work.

Marked by teacher Brady Smith 14/02/2012

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