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How does changing the concentration of the Hydrochloric acid affect it reactions with Magnesium?

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How does changing the concentration of the Hydrochloric acid affect it reactions with Magnesium? Aim: The aim of our investigation is to see how various solutions of Hydrochloric acid react differently to Magnesium. Introduction: The two main substances that will be used during this experiment are as follows: Hypothesis: I predict that as the concentration of the Hydrochloric acid increases, the time taken for the magnesium to disappear decreases. So, the higher the concentration of the acid, the faster the reaction between magnesium ribbon and the hydrochloric acid will be. This would be because there were more acid molecules to react with the magnesium ribbon. I also predict that when the concentration of the Hydrochloric acid doubles, the rate of reaction also doubles. (Therefore, hcl is directly proportional to mg, hcl ? mg. ) Increasing the concentration of the reactants will increase the frequency of collisions between the two reactants. So this is collision theory again. Kinetic theory is relevant. This is because the molecules in the reaction mixture have a range of energy levels. When collisions occur, they do not always result in a reaction. If the two colliding molecules have sufficient energy they will react. The atoms or molecules in a gas are very spread out. For the two chemicals to react there must be collisions between their molecules. By increasing the pressure, we squeeze the molecules together so you will increase the frequency of collisions between them. This is collision theory again. In the reaction between hydrochloric acid and magnesium ribbon, the hydrochloric acid will dissolve the magnesium and produce hydrogen gas. All chemical reactions involve reactants which when mixed may cause a chemical reaction which will make products. In my case the reactants are hydrochloric acid and magnesium ribbon. The chemical reaction takes place when the magnesium ribbon is dropped into the hydrochloric acid. The products that are formed during this reaction are hydrogen gas and magnesium chloride. ...read more.


I have decided to start readings at 20OC and increase by 10OC each time until 60OC is reached, since it will allow me to see the increase in rate of reaction and 5 results should be enough to identify any trends. * Rates of Reaction Increasing the temperature increases the speed of the particles. The faster the particles move, the greater the number of collisions, and therefore the rate of the reaction increases. A 10OC rise in temperature almost doubles the rate of most reactions. Chemical reactions take place by chance. Particles need to collide with enough velocity so that they react. As the temperature is increased the particles move faster since they have more energy. This means that they are colliding more often and more of the collisions have enough velocity to cause a reaction. Since there are more collisions the chemical reaction takes place faster. A tangent was drawn at the beginning of each curve and its gradient calculated, the gradients are shown in the table below. Evaluating Evidence I believe that the experiment was successful but some of the results were unexpected/unreliable. The lines on the graphs for 20OC and 30OC cross, this doesn't affect my results since I am only concerned with the initial rate or reaction but it was unexpected. In graph 3 the rate of reaction for 60OC is lower than that of 50OC - this result is anomalous and has been ignored in this investigation. I believe that the experiment was designed well but there were a few problems. Although the initial rate of reaction (which is what I am concerned with in this investigation) seemed to fit a trend, the rate of reaction curves of some temperatures on the graphs crossed. This could have been because some of the magnesium had corroded forming a magnesium oxide layer which would have affected the rate of reaction. Other factor which could have given me unreliable results could have been that the gas syringes were wet causing them to ...read more.


The graph gives us a good device to prove that if you double the concentration the rate would also double. If you increase the number of particles in the solution it is more likely that they will collide more often. There should be more H2 given off if we compare it across the range of temperatures because the reaction is going quicker and so more H2 is given off in that amount of time. There is more H2 given off if you compare it to the range of concentrations that you are using, this shows that the reaction is at different stages and so is therefore producing different amounts of H2. Also our results were not accurate but this could be because of a number of reasons. There our many reasons why our results did not prove this point accurately. � At high temperatures the acid around the magnesium starts to starts to dilute quickly, so if you do not swirl the reaction the magnesium would be reacting with the acid at a lower concentration which would alter the results. � Heating the acid might allow H Cl to be given off, therefore also making the acid more dilute which would also affect the results. � When the reaction takes place bubbles of H2 are given off which might stay around the magnesium which therefore reduces the surface area of the magnesium and so the acid can not react properly with it so this affects the results. To get more accurate results, we could have heated the acid to a lower temperature to stop a large amount of H Cl being given off. The other main thing that could have helped us to get more accurate results is we cold have swirled the reaction throughout it to stop the diluting of the acid and the bubbles of H2 being given off. If I had time I could have done the reactions a few more times to get a better set of results. This would have helped my graphs to show better readings ...read more.

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