area on rate of reaction | Reaction Rate | Chemical Reactions

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effect of area on rate of reaction
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  Introduction My investigation is about the rate of reaction. A rate of reaction is defined as how fast or slow a reaction takes place. For example, the oxidation of iron under the atmosphere is a slow reaction which can take many years, but the combustion of butane in a fire is a reaction that takes place in fractions of a second. For a reaction to take place particles must collide with sufficient energy; this is called activation energy. When temperature is increased the particles move faster and with more energy, therefore the collisions happen more often and with more force so the reaction is faster. Factors which affect Rates of Reaction: Surface Area  - Surface area is the measure of how much exposed area a solid object has, expressed in square units. Temperature  - Heating chemical substances can make the molecules separate and move around faster. This can increase the speed with which they mix with surrounding molecules from other chemical substances, thus speeding up a reaction. Concentration  – If solution contains high concentration of reactants, this means that more collisions would take place because there is more of a chance that the reactants would collide. On the other hand if a solution has low concentration, the chances of the reactants colliding is less, this increases the rate of reaction. Use of Catalyst  – If a catalyst is present then the reaction rate will increase due to the fact it replaces the amount of energy needed for the collision, allowing for more collisions to take  place. Aim: We will be investigating the rates of reaction when  sodium thiosulphate is crushed using mortar and pest le   To investigate the effect of surface area on the rate of reaction  TRIAL RUN  – How surface area affects rate Here the surface area of solid sodium thiosulphate was changed. Equipment used: ã Pestle and Mortar  – used to crush the sodium thiosulphate pellets to increase thesurface area ã Conical Flask   – used to put in hydrochloric acid into and mix with the crushedsodium ã Digital Stopclock   – used to time how long the crushed sodium mixed with thehydrochloric acid took to turn cloudy ã Safety Goggles  – to protect our eyes from anything going in them Safety:  To prevent accidents from occurring we took some safety procedures for this experiment: ã Fumes are dangerous so be careful with the reaction by opening windows. ã Liquids are corrosive so do not touch them and wash hands if touched. ã Safety goggles must be worn at all times during the experiment. ã Experiment should be handled carefully and slowly. Method: The method we used in this trial was to time how long it took for the small amounts of solid sodium thiosulphate pellets to react with the acid.   ã We measured 20g of sodium thiosulphate pellets ã We measured another 20g of sodium thiosulphate pellets however we crushed it withthe pestle and mortar to turn it into a powder  ã We added the sodium thiosulphate pellets into a conical flask containing 10ml of hydrochloric acid and recorded the time taken for it to fully react with the acid. ã Then a group member recorded the time. ã We added the powder thiosulphate to the acid and recorded the time for it to react.The person inspecting the sodiumthiosulphate remained the same; this was done so that the test was fair. Other variables were also kept controlled.  Results of trial run:  Surface area of sodium thiosulphate Mass (g) Volume of Hydrochloric acid (ml) Time taken to react (s) Sodium thiosulphate Pellets 20 10 60 Powder 20 10 6.51 This trial run proves the collision theory, it says that increased surface area increases rate of reaction Evaluation:  The results of this trial aren’t very accurate because enough data was not collected. This is  because it is difficult to measure surface area of tiny grains of sodium. Due to this, we managed to acquire only 2 results, powder and solid states of sodium thiosulphate. In addition, one other reason why the results were not that reliable was because we did not repeat this trial run more than once. We should have repeated the trial run more times to make the results more reliable and to see whether surface area does affect the rate of reaction. I compared my graph to another group’s to see the differences and to see if I had made any errors. It also would help me to draw the reasons for my anomalous results for example when the mass of sodium pellets was 20, my time was 60 seconds, but the other group’s time was 65 seconds; this helped me to detect any errors. On the whole this is a very subjective method e.g. crushing method is not very accurate. Also the reaction was completed when the pellets or powder had completely reacted, but because the solution got cloudy it became difficult to see. I will therefore to my trial run 1 as my final experiment. We decided to use the method which we used in trial run 1. We decided to use the trial run 1 method because we found the experiment easier to do rather than trial run 2 also; we found the measurement in trial run 1 to be more accurate than trial run 2. So, for our final run we agreed on measuring more levels of concentration; we started with 100% concentration and then reduced the concentration by 10% each time, this lead us to 10 levels of concentration. Each time while doing the experiment we reduced the amount of sodium thiosulphate on the other hand we increased the amount of water. We made sure the level of solution was level and we also kept the hydrochloric acid always the same. We made sure it was the same by measuring it with a measuring beaker.
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