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Investigating the rate of reaction between sodium Thiosulphate and hydrochloric acid

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Investigating the rate of reaction between sodium Thiosulphate and hydrochloric acid Introduction In this investigation, I am going to analysis the rate of reaction between Hydrochloric acid and Sodium Thiosulphate. When planning this investigation there were various ways in which I could have tested the rate of reaction. These included; changing the temperature of the chemicals or even adding different amounts of water/chemicals to the solution. I already know that when a dilute acid is added to Sodium Thiosulphate solution a pale white precipitate of sulphur is formed. This will allow me to know that a change has taken place. The equation for this is; Na2S2O3 (aq) + 2HCl (aq) _ SO2 (aq) + S(s) + H2O (l) + 2NaCl (aq) Equipment When carrying out thin experiment, I will be using the following: Beaker Cross drawn on paper, Diluted water, Hydrochloric acid (same concentration each time), Sodium thiosulphate (different concentrations), Measuring cylinders (One for each chemical), Safety goggles, Stop Watch, Thermometer. Variables To make the test fair I will have to change certain things and keep some the same. The variables I will be keeping the same are: Volume of Hydrochloric acid Volume of Sodium Thiosulphate Concentration of Hydrochloric acid Type of equipment (Same size cross, beaker etc.) Temperature of solution Through out the experiment we will only be changing the amount of water added and the concentration of Sodium Thiosulphate. ...read more.


We had to add the Sodium Thiosulphate and the water at the same time for this to be a fair test also. Like before we started the stopwatch when the two chemicals were mixed until the x couldn't be seen anymore. We repeated the experiment another two times in order to receive accurate results. Over these two I moved on to test 10cm3 of hydrochloric acid, 30cm3 of Sodium Thiosulphate and 10cm3 of water and so on adding 10cm3 of water each time and removing Sodium Thiosulphate each time until no sodium was left. Like I said in my prediction it took longer for the solution to become cloudy as it got more diluted. Results For each test I will use: Volume HCl (cm3) Volume Sodium T (cm3) Volume Water (cm3) Test One 10 40 0 Test Two 10 30 10 Test Three 10 20 20 Test Four 10 10 30 Test Five 10 0 40 Time taken: 1st Test 1st Re Test 2nd Re Test Test One 40.69 36.72 35.28 Test Two 45.56 41.13 40.03 Test Three 86.69 85.44 70.41 Test Four 143.82 144.65 135.69 Test Five Infinite Infinite Infinite Standard deviation Test One Results Observation x Deviation x-mean Squared Deviation (x-mean) 2 45.56 6.38 40.7044 36.72 -2.46 6.0516 35.28 -3.90 15.21 117.56 � 3 = mean = 61.699 S= V61.966 = 5.566237508 S=V5.566237508 = 2.3592975 Test Two Results Observation x Deviation x-mean Squared Deviation (x-mean) ...read more.


Evaluation I think most of the experiment I have done has been successful with as little un reliable results as possible. However, there are still a few problems with results which I will now point out. There was only one problem that occurred when looking at my recorded results. This may of happened due to basic human error or maybe because we measured the substances wrong. Apart from this little mistake I feel that all the rest of my results are accurate. Although we could of performed the experiment in different ways in order to make the test fairer and make the results more reliable. One way for this is by using different equipment each time in order to make sure there was no substance left in the bottom of the beakers or measuring cylinders. If I could repeat this experiment again I would change the volume of Hydrochloride acid so that it would now perform as the variable substance and have the Sodium Thiosulphate as the constant substance. This would allow me to add more evidence to support the idea of changing the concentration of the solution would affect its reaction time. Overall I think that this experiment was a successful as it proved that by changing the concentration of the solution it would affect the reaction time. The experiment has also showed me that even when the Sodium Thiosulphate is double the reaction time isn't always necessarily halved. ?? ?? ?? ?? Vicki - Louise Flowers General Science Coursework ...read more.

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