How the rate of reaction of Hydrochloric acid and Sodium Thiosulphate is affected by concentration? - page 1
Keywords: data analysis
By shaz on 08/02/2010
Level: GCSE Key Stage 4 (Years 10-11)
Page Number: 1 of 3 pages: 1 2 3
How the rate of reaction of Hydrochloric acid and Sodium Thiosulphate is affected by concentration?
Table of results
Volume of Sodium thiosulphate
(cm³) Time taken
for the cross to disappear (s)
5 440
10 140
15 110
20 65
25 54
Interpreting Data
There is a negative correlation between the rate of reaction and the time taken for the cross to disappear. As my input variable gets changes, my output variable tends to get smaller because as I increased the concentration of sodium thiosulphate the time taken for the cross to disappear is decreased.
My conclusion is that the more concentrated a reactant is, the quicker the
rate of reaction time will be. I have come to this conclusion because
of several reasons. My results give evidence that as the amount of sodium thiosulphate decreases and the amount of water in the solution, there are less atoms to collide and therefore less successful collisions causing chemical change so the reaction rate is slower. In a more concentrated solution, there are more atoms to collide with so the reaction time is quicker.
Collision theory
This happened because as I increased the concentration of sodium thiosulphate I also increased the amount of particles in a cm. Since there were more particles, they collided often making the reaction process quicker. Increasing the concentration of a solution leads to more collisions (greater frequency of collisions) so the rate of the reaction goes up.
Evaluation
The experiment was carried out within one day and it took one hour which was good because the light intensity was roughly the same therefore providing more accurate results. Whereas, if it was done over a longer period of time the light intensity could have changed and made it much easier or difficult to see the cross making it an unfair test.
If I were to complete the experiment again I would use a smaller measuring cylinder to measure the volume of sodium thiosulphate, water and hydrochloloric acid. I think by using a 50cm³ measuring cylinders I reduced the level of accuracy in my results because the measuring scale lines were larger and probably less accurate. I think if I was to improve my results I would use a much smaller measuring cylinder, this will ensure I have used a more precise amount of water, sodium thiosulphate and hydrochloric acid. To make the results more accurate I would use a more precise stopwatch.
I would investigate the reaction between 5cm3 and 10cm3 in more detail because the time taken for the cross to
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