Chemistry
...look at hydrochloric acid and sodium thiosulphate which is a precipitation reaction. They react as in the equations below:
Sodium thiosulphate + hydrochloric acid -> sodium chloride + sulphur + sulphur dioxide + water
Na2S2O3(aq) + 2HCl(aq) -> 2NaCl(aq) + S(s) + SO2(g) + H2O(l)
Prediction:
My prediction for the experiment of mixing the 2 compounds Sodium thiosulphate and hydrochloric acid together is when the higher the concentration of sodium thiosulphate the shorter the time it will take for the reaction to be completed in are case for the cross not to be visible. Where as the lower the concentration the longer it will take for the reaction. A reaction will only occur where the particles of the reactants meet and combine. This is called the collision theory. Therefore it stands to reason that to increase the rate of reaction it is necessary to cause more particles to collide harder and make it happen more often. There are several ways to do this and these make up the variables for this experiment. They are listed below along with predictions as to their affect on the reaction.
Increasing the pressure. By reducing the volume in which the same amount of particles exists the pressure is increased. Once the same number of particles is in a smaller area there is less space in which to move and so the particles are more likely to hit each other. It is therefore possible to predict that increasing the pressure will result in an increase in the rate of reaction. I will not test this variable because the school doesn't have the facilities to test it. However pressure is a continuous variable.
Using a catalyst is another method that could affect the time. A catalyst is a separate substance which speeds up a reaction. After the reaction has happened it gets left behind. This makes this variable unsuitable for the type of experiment I am going to do. A catalyst...
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