investigate the effects of temperature on the reaction between sodium thiosulphate and hydrochloric acid.

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Science Coursework: Rates of Reaction
Skill section P


Aim:
 To investigate the effects of temperature on the reaction between sodium thiosulphate and hydrochloric acid.

 Scientific Knowledge:
Reaction: When atoms or groups of atoms re-arrange resulting in the change of molecular structure in substances, is only possible when the particles collide with the other reactants with enough energy to form the transition state and change it into other products. Without such circumstances reaction will not be possible. This is collision theory.
The factors that affect the rate of reaction are:
-
Temperature 
-
Pressure
-
Size of surface area in which reaction will take place
- The
concentration of reactants

The reaction will take effect faster if any of these are increased. That is all because of collision theory. Reactants also need to have sufficient energy, activation energy, to react. If increasing
temperature, the reactants will vibrate more making it more likely for them to collide and collide harder as they have more energy, meaning that they will have the activation energy to make reaction more likely. If pressure is high then there is more chance for the reactants to collide as they will be closer to each other. If surface area is increased then more reactants can collide with each other as there is more space for collision. When there is a higher concentration of reactants there is more chance of collision as there are more reactants to collide with. In effect, making collision easier makes reactions faster whilst hindering collision will only slower rate of reactions.

Sodium Thiosulphate + Hydrochloric acid
 Sodium chloride + water + sulphur dioxide + sulphur

Na2 S2 O3 + 2HCl 2NaCl + H2O + SO2 + S

 
The sulphur that is formed is a white, insoluble precipitate, which turns the solution cloudy. Although the Sulphur is white in the solution, it is usually yellow. We will use this to help us see when the reaction begins and ends. As soon as the cross on the white tile underneath the conical flask (which contains the solution) disappears, we will stop recording because the reaction is over.

Prediction:
I predict that the higher the temperature the faster the reaction, which also means, the lower the temperature the slower the reaction (they are indirectly proportional). I also predict that the higher the temperature, the faster the rate of reaction (they are directly proportional). This is because of the collision theory, as said in my Scientific Knowledge, stating that with sufficient activation energy and collisions, reaction will occur. I will use my preliminary test to support my prediction.

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Preliminary test:
 
The reaction taking place is sodium thiosulphate with hydrochloric acid in different temperatures. I am using different molars as I want to test which one would make the solution react faster, but also prove that the higher the temperature, the faster the reaction, and vice versa as stated in my prediction. I don’t want the temperatures to increase/lower to room temperature, as it wouldn’t prove much. Therefore, looking at my preliminary test, the molar used will be 1 for my actual experiment.

Collision Theory when particles are heated:

 

Fair test:
I will be keeping all the factors that ...

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