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How the concentration of Sodium Thiosulphate affects the rate of reaction with Hydrochloric Acid.

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How the concentration of Sodium Thiosulphate affects the rate of reaction with Hydrochloric Acid Plan We will set up a conical flask on top a cross. We will vary the concentration of Sodium Thiosulphate by putting different amounts of Sodium Thiosulphate and water bye keeping the same total volume of 50cm�. We will then add 5cm� of hydrochloric acid. We will time how long it takes for the cross to completely disappear from site after the reaction has completely finished. Constants Variables Temperature Concentration of Sodium Thiosulphate Total amount of Sodium Thiosulphate + Water Size of conical flask Amount of hydrochloric acid Hydrochloric acid concentration Same person seeing when the cross disappears completely Experiment Prediction If the concentration of sodium Thiosulphate is change I predict that the rate of reaction will change. The higher concentration of Sodium Thiosulphate per cm� the quicker the reaction will take place. This is because the more Sodium Thiosulphate particles there are, the more chance, and the more successful collisions with Hydrogen+ ions in the Hydrochloric acid will be. I predict that if the concentration is doubled the rate of reaction will double. ...read more.


This means that when the concentration of Sodium Thiosulphate doubles, the reaction takes place twice as fast. This is because when the concentration doubles, the amount of Sodium Thiosulphate particles doubles, so collisions of Sodium Thiosulphate and Hydrochloric acid ions occurs twice as often. This means that the reaction is complete twice as quick, and the liquid will cloud up so we can't see the cross in half the time. For example when the volume of Sodium Thiosulphate was 20cm� and volume of water was 30cm�, the result for 1/time was 0.009s . And when the volume of Sodium Thiosulphate was 40cm� and volume of water 10cm�, the 1/time result was 0.018s . This is double the speed of half the concentration. Particle diagram: This shows that twice the amount of Sodium Thiosulphate particles there are the twice as likely they are to hit and react with a Hydrochloric acid ion to complete the reaction and make the cross disappear from site. Sodium Thiosulphate + Hydrochloric acid � Sodium Chloride + Sulphur + Sulphur dioxide + Water Na2S2O3 (aq) ...read more.


We may have been at different angles looking down on the cross through the solution which would mean that the cross may seem to disappear from one angle but may be still seen from another angle. To improve the reliability of the experiment we could put a light under the conical flask, instead of a cross. And use a light sensor attached to a computer program which would stop timing when the light had disappeared. The light would have to be quite dim otherwise it may shine through the liquid even when it had clouded up. It would also have to be done in the dark so that there is no interference from other light sources. We could improved the reliability of the experiment by using more accurate measuring equipment, such as a syringe to measure the liquids. We could extend our work further by using other acids besides Hydrochloric acid and note if there is any difference in time, if any. We could add a catalyst and vary the amount or size of the catalyst bits and not change the amounts of each solution. We could vary the temperature of the experiment by heating or cooling the Sodium Thiosulphate mixture and note the time for the same concentration. ...read more.

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