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Sodium Thiosulphate Investigation

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Sodium Thiosulphate Investigation Introduction: This is an investigation into the reaction speeds of Sodium Thiosulphate [Na S O] under different conditions. We will be using a catalyst, which is Hydrochloric Acid [HCl]. Na S O + HCl ==> 2NaCl + SO + S + H O When the two chemicals are mixed the Sulphur slowly forms as a solid, but it does not precipitate out in the usual way. The time for a given amount of reaction can be found by checking the cloudiness of the mixture. The way in which we can find out the rate of reaction is by timing the reaction and finding out how long it takes for the liquid to become opaque under the conditions we set, then we divide the change by the time. Then we will find out the effect of one factor on the reaction by only changing one input variable and keeping the rest constant. There are 5 variables for rate of reaction, Surface Area, Catalyst, Pressure, Concentration and Temperature. But only 3 of these are applicable to this experiment, Concentration, Catalyst and Temperature. Rate = A Chemical Change Time Taken A reaction happens when a successful collision occurs between 2 particles. For a successful collision to happen the bonds in each particle need to be broken so a new product can be made, and to do this it requires a certain amount of energy is needed. The energy in the collision is in the form kinetic energy when the 2 particles collide. ...read more.


This is the closest size to the amount being measured so will be easiest to measure it accurately. * 1 x 10cm measuring cylinder to measure the correct amounts of HCl, again 10cm is the amount we need so this will be the easiest and most accurate to measure it with. * Safety Goggles, to protect your eyes from the harmful chemicals, if something does get in your eye wash it quickly with clean water then report it too the teacher * Lab coat, this is in case any chemicals are spilt, this will protect from the harmful ones. Again report spillages to the teacher in charge. Preliminary Data: CONCENTRATION OF Na S O TIME TAKEN in SECONDS 40cm 0cm water 30 20cm 20cm water 50 10cm 30cm water 120 6cm 34cm water 220 4cm 36cm water 330 We have decided that the range should be from 10% to 50% because at 10% it approximately 5 minutes and at 50% it takes approximately 1 minute, so this range is good for this experiment in the lab because if the time was any faster it would give unreliable results and if it were and slower we would not have enough time to complete the experiment in the laboratory. Method: 1. Make sure you are wearing safety goggles and a lab coat to protect yourself from the chemicals, because they can corrode or burn skin. 2. Collect the apparatus needed and set up as shown in the diagram below. ...read more.


There are no anomalous results because all the points on the graph fit the line of best fit and they all follow this same pattern so they are all reliable. The practicality of the experiment is quite easy to perform, but some features do make it difficult to take very accurate readings. The dot underneath the beaker in which the reaction takes place would sometimes vary in size and in shade of black. Using the same dot for every reaction could help this. The beaker would pick up a residue of Sodium from the reaction, which would make the beaker seem slightly cloudy to start with, so after a few reactions the beaker would begin to build up quite a thick residue, this could be helped by either using a different beaker for each reaction or by cleaning the beaker thoroughly. Also the light can effect how easy it is to see the dot through the liquid, if there is a bright light in the lab then it will be easier to see the dot through the liquid, so it will take longer the for the dot to be obscured. You could use a light meter to check that the light is always the same when you check for the dot to be obscured. I don't feel the evidence is fully reliable, because there are at least 3 things that can be done next time to improve the experiment, I also feel that there is always a margin of human error, but this is hard to eliminate. I think also that taking more results would help to make the graphs and conclusions more reliable. Matt Barnes 10-2 Dr. Cruise ...read more.

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