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Investigating the Reaction Between Sodium Thiosulphate and Hydrochloric Acid

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Investigating the Reaction Between Sodium Thiosulphate and Hydrochloric Acid P O A E Name: Group: Teacher: Candidate Number: Centre Number: References In order to understand the experiment better, and to get more accurate results, I used the following sources for extra information: * Science to 16- Pople and Williams, Page 19 * GCSE Chemistry- Earl and Wilford, Chapter 11 * www.schoolchem.com/rc4.htm Planning 1) Research a) Measuring the Rate of Reactions The rate of reactions can be measured by either tracing the lessening of the reactant, or the development of a product. b) What is the collision theory? A reaction can only happen between particles when they collide. Particles have to collide with enough force in order for a reaction to be possible, as if they do not collide with enough power, the particles merely rebound off each other, and so no reaction can take place. Particles have more energy the faster they are moving, and therefore the collision rate increases. Particles move faster when the temperature is increased. c) How can we change the rate of a chemical reaction? There are five ways to increase the reaction rate. These are: 1) Increasing the temperature 2) Increasing the concentration 4) Increasing the surface area of a solid (e.g. a powder has a larger surface area than a block) 5) Use a catalyst. The reaction rate can be decreased by: 1) Decreasing the temperature 2) Decreasing the concentration 4) Decreasing the surface area of a solid (e.g. a block has a smaller surface area than a powder) 5) Not using a catalyst. d) What is a 'catalyst'? ...read more.


- Repeat the experiment for various volumes. oOOOO 3) Diagrams 4) Predictions I predict that the rate of reaction will increase as the volume of sodium thiosulphate is increased. However, I think that as the volume of sodium thiosulphate is decreased, the reaction rate will also decrease. I think this because it is the sodium thiosulphate which makes the solution become opaque, and therefore the more of this substance is included, the faster the solution should go cloudy. When the amount of hydrochloric acid exceeds the amount of sodium thiosulphate, the sodium thiosulphate will be unable to work as quickly, as it will take longer for the hydrochloric acid particles to combine with a sodium thiosulphate particle. 5) Fair Testing - Only one variable should be changed per experiment - The same conditions should be kept, where possible, throughout experimentation e.g. heat (if the variable being altered is not temperature), light etc - Keep the intervals between the amounts of each chemical different i.e. change the amount of each by 5cm3 or 10cm3 each time - Do not mix the sodium thiosulphate and hydrochloric acid together until there is the required amount of each substance, and the required conditions have been met - Start the stopwatch at the same point in each experiment - The same person should watch the cross each time (if the experiment is to be conducted in groups) 6) Safety Rules - Goggles must be worn at all times - Long hair must be tied back - All stools and chairs must be pushed under desks or out of the way - All coats and bags should be put away properly and out of the way - No running in ...read more.


Explain how the evidence collected is good enough to make an accurate conclusion? The results achieved were as fair as possible, and as human error was greatly reduced, quite reliable. Only one variable was altered for each experiment, and this was changed in equal amounts. The stop watch was stopped the second tat the cross was no longer visible, and so in precisely the same point on each test. The substances were, obviously, not mixed prior to the experiment, and so worked to their maximum potential. Describe, in detail, further work that you could do to provide additional evidence? In order to provide more evidence, I could perform the experiment manually. This way, I would have slightly more options open to me, as there were limited choices on the computer. For example, if I performed the experiment manually, I would have the opportunity to lower the temperature using ice, or heat it up to 100�c to get a wider range of results. I would also be able to experiment with different volumes of sodium thiosulphate more freely. I could also experiment with altering different variables, such as different concentrations of hydrochloric acid, in order to see what would happen to the reaction time. Also, I could perform other experiments to see how reaction rates change. I could do the other two experiments discovered in my research: the reaction between calcium carbonate and dilute hydrochloric acid, and the disintegration of hydrogen peroxide solution. This would tell me if the patterns for rates of reactions remain the same for all experiments, rather than just one, or what the differences between the rates of reactions are, nd why they are different. Page 1 of 14 ...read more.

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