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What affects the rate of reaction between Sodium thiosulphate and Hydrochloric acid

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What affects the rate of reaction between Sodium thiosulphate and Hydrochloric acid? Introduction A chemical reaction can only happen if the molecules frequently and successfully collide into each other. These molecules have to hit each other in the right direction and at the right speed and with the right amount of energy. Prediction I predict that the more concentrated the acid the faster the rate of reaction. Theory to back up my prediction Particle theory tells us that the more particles the more frequent successful collisions there will be. When the concentration of the acid is increased the rate of reaction increases because of more successful collisions. Low concentrated acid High concentrated acid Variables: The rate of reaction depends on four things * Catalyst- A catalyst speeds up the rate of reaction without using itself, giving the particles a surface to stick to so they are able to have more frequent collisions. * Concentration -Concentration of a reactant affects reaction rate because there are more frequent successful collisions. ...read more.


I will take the results in seconds and then calculate the average time for the reaction to happen. Method 1. On a plain piece of paper draw a black cross. 2. Then place the beaker on top of it. 3. Measure 25ml of hydrochloric acid into the measuring cylinder. 4. Add the 25ml hydrochloric acid to the sodium thiosulphate. 5. Start the stop clock when both the hydrochloric acid and sodium thiosulphate have been poured into the beaker. 6. When the cross is no longer visible stop the stop clock. 7. Wash the beaker thoroughly and repeat steps 2-5 another two times. 8. Repeat steps 2-6 with different with different hydrochloric acid molar strengths : Molar Strength of Hydrochloric Acid Volume of 2 molar Hydrochloric Acid in (ml) Amount of Water Added (ml) 2 50 0 1.60 40 10 1.20 30 20 1 25 25 0.80 20 30 Results Table Molar Strength Volume of 2 molar Hydrochloric Acid Water (ml) ...read more.


Looking at graph A you can see that there is a positive correlation between the concentration of hydrochloric acid and the reaction rate. When hydrochloric acid and thiosulphate react together the sulphur is stronger of the two. This means that as the reaction goes on the solution becomes yellow and will change from being transparent to translucent to opaque. The more concentrated the acid the more particles there are which means the more collisions. I can finally conclude that as molar strength of hydrochloric acid is increased so is time taken. Evaluation The results supported my predictions and they seem to be fairly reliable and accurate, as there weren't any anomalous points. If I were to repeat this experiment I think that I could improve my results even more by * I don't think there was a large enough range of results taken so I would increase the number of experiments another twice for each category * Repeat experiment but with a different person to judge when the reaction has finished. * Make sure apparatus and equipment is washed thoroughly. * Make sure not to contaminate either chemicals. ...read more.

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