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Rates of Reaction

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Rates of Reaction Planning Aim: We are planning to find out how different factors affect the rate of two chemicals reacting, Sodium thiosulphate and hydrochloric acid Factors: There are a range of factors which will affect the rate of this reaction between two chemicals. Such as: Temperature Concentration of reactants Presence of a catalyst Pressure Temperature: When substances are heated the particles take in energy this causes them to move faster and collide more often. These increased collisions also have more energy so they are more likely to be successful. Concentration: If the concentration is higher there are more acid so a collision is more likely to occur with more collisions there is a higher rate of reaction. Catalyst: If there is a catalyst present the reaction will be speeded up because less energy is needed for a collision to be successful. This means that more collisions become successful, so the reaction goes faster. Surface area: The reaction is faster when there is a larger surface area because more atoms are exposed. ...read more.


This is because the ions are closer together in a concentrated solution. The closer together they are, the more often the ions collide. The more often they collide, the more chance they have of reacting. Method: I will create the correct concentrations of acid. We are given two concentrations of acid to start off with. 50g per litre and 60g per litre. We then need to mix the two together to create 3 other different concentrations. To measure the rate of the reaction we will put the two solutions together in a conical flask and by timing from the start to when the cross is no longer visable we can determine the speed of the reaction. The two solutions are translucent but when they are mixed sulphur if form and creates a sediment which covers the cross. I will have to take three repeat result to ensure accuracy. This reaction is: Na2S2O3 + 2HCl --> 2NaCl + H20 + S + SO2 The sulphur is the thing which shows us the rate. ...read more.


This is because a higher concentration means a larger number of particles in a given volume. If there are more particles, there will be more collisions. More collisions means a larger number of successful collisions. Therefore the reaction rate will increase. As what is needed for a successful collision (The collision theory) is that particles must collide and the colliding particles between them must contain enough energy to cause bonds to break. Therefore my prediction was correct "If I increase the concentration of the acid the speed of the reaction will increase" Evaluating Evaluation: My results are accurate the reason for the slight anomaly in the curve of the graph is the uneven interval of the concentrations. To improve the experiment I could have used a LDR (light dependant resistor) which is more accurate for measuring when the cross is covered by sediment then the human eye which is subject to error although the same LDR would have to be used each time as they have different tolerances to light. I could have used a 1/Time graph which would give me a straight line and show how 1/Time is directly proportional to the concentration of the acid. ...read more.

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