The effect concentration of hydrochloric acid has on the rate of reaction -- A* - page 1
Keywords: Rate of reaction hydrochloric acid sodium thiosulphate concentration
By georgie1 on 31/12/2009
Level: GCSE Key Stage 4 (Years 10-11)
Page Number: 1 of 8 pages: 1 2 3 4 5 6 7 8
How does the concentration of hydrochloric acid affect the rate of reaction when added to sodium thiosulphate?
Investigation to find out how the rate of reaction is affected when concentration of a solute is varied
The aim of my experiment is to discover what factors affect the rate of reaction of hydrochloric acid when it is added to sodium thiosulphate.
Reaction:
Na₂S₂O₃ + 2HCl → 2NaCl₍aq₎ + S₍s₎ + SO₂₍g₎ + H₂O₍l₎
Sodium thiosulphate + Hydrochloric acid → Sodium chloride + Sulphur + Sulphur dioxide + Water
The output variable that I shall be recording is rate of reaction which can be calculated using the following formula:
Rate of reaction = 100 _
Time (secs)
The possible input [independent] variables that I could have changed are temperature, surface area, concentration and use of a catalyst. I have chosen to vary the concentration of the hydrochloric acid as my input variable because it is the easiest to monitor and measure in comparison with the other options. The concentrations I am going to be using are 0.0M, 0.2M, 0.4M, 0.6M, 0.8M and 1.0M. By using this range, I will obtain more precise results because I will be able to see my results in closer detail. If I was to change the temperature, the results would be difficult to collect accurately because it would potentially be difficult to get all experiments to the same temperature. Therefore, they may not show significant patterns in my results. If I was to change the surface area, accuracy would also be difficult because I cannot change the size of the molecules in the two liquids. However, if I was to be using a solid as one of the reactants, particle size may be easier to measure because I would be able to change the sizes by cutting them etc. If I was to use a catalyst to see how the rate of reaction was affected, I would not be able to draw any quantitative conclusions because there would be no measurements for the additional substances other than names. As a result, the factors that I will control are:
• Temperature of the solution. To keep the temperature consistent, I am going to ensure that the room is kept at a consistent temperature and experiments positioned the same distance away from heaters etc. This is so that the particles do not gain kinetic energy, causing faster collisions and therefore, a faster rate of reaction. As
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