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Factors that affect the rate of a reaction.

Extracts from this document...

Introduction

Factors that affect the rate of a reaction INTRODUCTION The rate of a reaction is how long it takes for the products in a reaction to form or how rapidly the reactants get used up. It is possible to tell something is reacting because odours and gases are given off, there can be a change in colour, change in ph level, fizzing and bubbling. A reaction will happen fastest at nearer the start of the reaction because this is when there is the most amounts of reactants, as the reactants get used up the rate of reaction is slower. The rate of reaction is found by measuring the amount of a reactant used up per unit of time or the amount of a product produced per unit of time. A reaction can be made to go faster or slower by changing a number of factors. In order for a reaction to occur it is required that: particles must collide with each other and the collision must have enough energy. If this happens the original bonds are broken and new bonds are formed so that new products are formed. The collision theory is related to the rate of a reaction. When collisions occur, they do not always result in a reaction. If two colliding molecules have sufficient energy they will react. This is called the 'activation energy'. Successful collisions can be increased by a number of factors. These factors include: * Temperature - By heating the mixture the energy levels of the molecules involved in the reaction are increased. Increasing the temperature means the molecules move faster because more energy is being transferred to them (kinetic theory) ...read more.

Middle

I will now clarify if 3g is the right amount to choose by trying it in 50ml of a 1M solution and 2M solution to get an idea of how quickly it reacts: - After five minutes the amount of gas released in a 1M solution was 243CO/cm � and in a 2M solution it was 462CO2/cm �. 3g also gives off quite a lot of gas in the more concentrated solutions. This shows that 3g also reacts too fast so I will again decrease the amount of calcium carbonate. I will now try 1g of calcium carbonate in 50ml of a 2M solution to get an idea of how quickly it reacts: - After five minutes in a 1M solution the amount of gas released was 65CO2/cm � and after five minutes in a 2M solution there was 157CO2/cm �. For my actual investigation I will need to collect around at least eight results for a more accurate conclusion. I will do this by measuring the volume of gas at 30 second intervals over a period of five minutes; this will give me ten results. From my preliminary work I have gathered that using 1g of medium sized marble chips is the most reasonable amount to use in the actual investigation because it does not react too quickly so it will give me a good number of results to conclude from. As I have used 50ml of hydrochloric acid so far I will continue to do this in the actual experiment. From the preliminary work I have also decided that I will also repeat the experiment three times, instead of once, using each concentration of solution for more reliable results. ...read more.

Conclusion

This reduces the reliability of the experiment because some gas may have escaped when the measuring cylinder was being changed. Another factor that may have affected the fairness of the experiment was half of the experiment had to be carried out on a different day so the temperature (one of the controlled variable) may have been slightly higher or lower during the different days. Also the size of each marble chip that made up 1g was not all equal, this affects the surface area (another controlled variable for this investigation). To increase the reliability of the investigation I could have collected more data by doing the experiment, for each concentration of solution, several more times to get a more accurate overall average. I could have done this by doing the experiment for longer than five minutes, by doing this I may have also seen the reaction beginning to slow down or even stop: Unlike my predicted graph, on my actual graph there is no definition of where the reaction begins to stop or even slow down and I may have seen this happen on the actual graph if I continued the experiment for a longer period of time. I could have also investigated more concentration of solutions, for example 1.5M and 2.5M. I would be able to depict a more profound conclusion and it would also make my conclusion more validated. Also, when calculating the average I could also have rounded it to 2 or 3 decimal places, instead of 1 decimal place, to increase the accuracy of my calculations. However, my results seem to be accurate and there are no anomalous results according to the line of best fit on the graph. This means there was possibly the least amount of experimental errors during my experiment. 1 ...read more.

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