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Aim/Introduction
My aim is to undergo an investigation to conclude whether the concentration of Sodium Thiosulphate affects the rate of a chemical reaction.
“The rate at which a reaction takes place depends on a number of factors. Several things can be done to either speed up or slow down a chemical reaction. These are:
Changing the surface area of any solids involved in the reaction
Changing the concentration of any reactants that are in a solution
Changing the pressure in reactions where gases are involved
Changing the temperature of the reaction mixture
Adding a catalyst“. (AQA GCSE Science)
Prediction/Hypothesis
I predict that the reaction rate will be faster at elevated concentrations. I hypothesise this for the reason that the higher concentrated Sodium Thiosulphate will contain more particles, which will crash into each other more frequently than if there were less particles because of the lack of space. ...
This theory can also be used to explain the differences between the different states (or phases) of matter. ...
Gases
“The average distance between particles typically 10 times greater than in solids and liquids. ... edu)
Seeing as the particles will be crashing against one another, this will act as a catalyst, generating more energy, consequently speeding up the reaction rate. Accordingly, with the higher concentrations, the Sodium Thiosulphate will change colour speedily than the Sodium Thiosulphate solutions with weaker concentrations. ... The relationship between the diffusion and the mobility of the dissolved substance in the solvent is also to be found. ... Thus, the relationship between the path described by solute particles in a solution and the process of diffusion had been established.
According to the molecular kinetic conception, there exists no essential difference between a solute molecule and a suspended particle. ...
Apparatus
Conical Flask
Sodium Thiosulphate
Paper
Ruler
Measuring Cylinder
Black Biro
I will set up the apparatus as shown on the next page. ...
Plan/Method
I firstly cleaned a measuring cylinder and filled it with 20cm3 of the Sodium Thiosulphate solution. ... I poured the Sodium Thiosulphate solution into the conical flask and I was now set in proceeding with my experiment. ... One of the people in my group would time the reaction and another would observe the “X” over the solution until he could see it no longer. ... The person watching the “X” noticed that it had disappeared because a chemical reaction had occurred.
The equation for the reaction that has occurred is:
Na2S203 (aq) + 2HCl (aq) ? 2NaCl (aq) + H2O (l) + SO2 (g) + S (s)
Within my investigation, the concentration amounts used were 10 grams, 20 grams, 30 grams, 40 grams and 50 grams of Hydrochloric Acid. Reiterating the experiment with the Sodium Thiosulphate at numerous concentrations, I feel was an extremely good procedure in helping me to answer and conclude my aim.
The independent variable of the experiment was the concentration of the Sodium Thiosulphate solution. The dependent variable was the time it took for the Sodium Thiosulphate to react with the Hydrochloric Acid and change colour so the “X” mark was no longer visible.
Approximate Word count = 2443
Approximate Pages = 9.8
(250 words per page double spaced)
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