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Rates of reactivity.

Extracts from this document...

Introduction

Introduction Rates of reactivity The rate of reaction is simply how fast it takes for a complete reaction to occur. In this coursework the following factors will be investigated to discover whether or not they affect the rate of reaction: * Surface area of reactants. * The temperature of reactants. * The concentration of reactants. * The involvement of a catalyst in a reaction. Collision Theory This states that reactions only commence when reacting particles collide with each other with a sufficient amount of energy, the minimum amount of energy. When the temperature of the reactants is increased particles absorb energy and move around a lot faster. This increases the chance of collisions. Increased concentration leads to more reactive particles and therefore more chance of collisions, increasing the rate of reactivity. Small pieces of reactants mean a large surface area. This allows more collision to take place resulting in a faster rate of reaction. Catalysts allow particles to react with a lower amount of energy. They also provide a surface for the particles to attach to; therefore the chances of collisions are higher. What is meant by rate of reaction? Magnesium + Hydrochloric Acid Magnesium Chloride + Hydrogen Mg (s) + 2HCl(aq) MgCl2 (aq) + H2 (g) In order for the magnesium and acid particles to react together, they must have the following bullet points present: * They must collide with each other. * The collision must have enough energy for the reaction to take place. Acid particles Water molecules Magnesium atoms The particles in the liquid move around continually. Here an acid particle is about to collide with a magnesium atom. Here the reaction is taking place. If enough energy is present then the reaction would take place and magnesium chloride and hydrogen will be formed. Acid particles Water molecules Magnesium atoms If not enough energy is present then the will be no reaction. ...read more.

Middle

* When the magnesium strip is dissolved the stopwatch is stopped. * Three trails are taken to obtain accurate results via an average. * The results are recorded on a table. * The test of suspended in a water bath of plain water. * Then we light the Bunsen burner. * Then we get the test tube out the fridge and check the temperature. * When the temperature is exact 200c, we add a magnesium strip to the acid. * When the magnesium strip is dissolved then we stop the stopwatch. * The result is recorded on a table. * We do the same every time, but we increase the temperature by 200c. * We record the results up to 1000c. Results The table shown on the next page shows the results that are based on the temperature experiment: Table 3b Temperature Degree Celsius Trial 1 Time taken (Seconds) Trial 2 Time taken (Seconds) Trial 3 Time taken (Seconds) Average Time taken (Seconds) 100c 59 60 61 60 200c 54 55 56 55 300c 54 55 56 55 400c 52 53 54 53 500c 47 48 49 48 600c 45 46 47 46 700c 39 40 41 40 800c 36 37 38 37 This data is shown on graph 2b on the next page: Factors affecting the rate of reaction Concentration Planning Aim My aim in this part of the coursework is to find whether or not the rate of reaction increases when the concentration of a reaction is increased. I must produce a piece of coursework investigating the rates of reaction, and the effect different chances have on them. The arte of reaction is the arte of loss of a reactant or the rate of formation of a product during a chemical reaction. It is measured by dividing 1 by the time taken for the reaction to take place. There is five factors which affect the rate of a reaction, according to the collision theory of reacting particles: temperature, concentration, pressure, surface area, catalyst and concentration. ...read more.

Conclusion

When the temperature was 300c and 500c the time taken increased. This may have been due to many reasons. Improvements, which could have been made: * Could have started with a lower temperature. * Use pure magnesium filings to increase surface area and increate the rate of reaction, which should give a greater variation between concentration; this will give a better result for the temperature experiment. * Make sure that non-oxidised magnesium strips are used to give more accurate results. * Control the temperature of the surrounding by encasing each experiment to prevent any changes in temperature at the start of the reaction to the end of the reaction form affecting the experiment. Extensions that can be carried out after the investigation After this experiment was done, I had realised that I could have taken the following points under consideration to make it a better investigation: * More concentrations of acid could be used to see if they have similar affects on the temperature rise. * Different substances could be reacted to see if they behave similarly. * More repeats could have been carried out to qualify the findings. These could be done under different conditions to see how the reactions react under a colder or hotter environment. Inaccurate results During the experiment we can see that many results were wrong and did not fit the line of best fit. There are some reasons to why they may have gone wrong: * When doing the experiments there is an internal energy that may have affected the results. This is known as Enthalpy. When we heat the sulphuric acid we measure the temperature not the internal energy. It is very hard to control and measure the Enthalpy. The internal energy measures the amount of heat present inside the chemical compound. * When doing the temperature experiment convection in the sulphuric acid affects the water current. There is a chance that the reaction could go faster or slower. * When doing the surface area experiment the sizes of the calcium carbonate chips were not the same. This may have affected the results. ...read more.

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