Rate of Reaction Investigation
Rate of Reaction Investigation
Planning
In this investigation I will find out what affects the rate of reaction of sodium Thiosulphate - Na2S2O3 - and hydrochloric acid - HCl - and will explain the behaviour of the reactants.
Na2S2O3(aq) + 2HCl(aq) + 2NaCl(aq)+ SO2(g) + S(s) + H20
Sodium + Hydro- + Sodium + Sulphur + Sulphur + Water
Thiosulphate chloric Chloride Dioxide
Acid
First, I will list all the factors that would affect the rate of reaction in this investigation.
* Temperature - hotter particles become more active and create faster collisions.
* Concentration of reactants in solution - amount of particles of reactants in solution would vary the rate of reaction.
* Volume of solution(s) - the volume of the solution may affect the rate of reaction, by having more or fewer particles colliding in the solution.
* Surface area - this factor does not apply in this investigation because there are no solids involved.
* Pressure - amount of pressure may vary on a barrier (should one be placed on top of the reacting solution) that would prevent Sulphur Dioxide from leaving the solution. Not applicable in this investigation.
* Catalyst - a Catalyst will not be used in this investigation therefore this factor is not applicable.
The factor I am going to investigate will be:
* Temperature.
But before I begin those experiments investigating temperature, I will conduct some preliminary experiments. The factor I will investigate in these will be:
* Concentration of reactants in solution.
Before I begin the experiments, I am going to predict the results.
I predict in the preliminary experiment the reaction rate will decrease as the concentration of dissolved reactants decreases, because there will be a lower concentration, therefore fewer particles to collide, thus giving a slower reaction rate.
And I predict that in the main experiment the higher the temperature, the faster the rate of reaction because the particles will become more active and faster, causing faster and stronger collisions, as shown below:
Factors that will need to be controlled in this experiment are:
* Temperature - because depending on the temperature, the collision of the particles will be faster or slower, so the temperature needs to be controlled or the experiment would be unfair. We will determine which is the most suitable temperature for the experiment from our results.
* Concentration of ...
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And I predict that in the main experiment the higher the temperature, the faster the rate of reaction because the particles will become more active and faster, causing faster and stronger collisions, as shown below:
Factors that will need to be controlled in this experiment are:
* Temperature - because depending on the temperature, the collision of the particles will be faster or slower, so the temperature needs to be controlled or the experiment would be unfair. We will determine which is the most suitable temperature for the experiment from our results.
* Concentration of reactants in solution(s) - this is a variable I have chosen to analyse, so it would be controlled, but varied.
* Volume of solutions(s) - this will have to be kept equal at all times to give a fair test, otherwise there would be an uncontrolled factor that would have a varied amount of particles colliding.
* Surface area - this is, as stated before, a factor that doesn't apply to this experiment.
* Pressure - this factor would only apple should there be a barrier over the reacting solution, where a varying amount of pressure would be applied by that barrier on top, therefore preventing any sulphur dioxide being released, and making the results unfair. This factor will be controlled by simply not having a barrier on top of the reacting solution.
Prediction
In my preliminary experiment I predict the reaction times will increase as the concentration of water goes up, and concentration of sodium thiosulphate solution goes down, therefore the best concentration will be with the highest sodium thiosulphate concentration. And in the main experiment, I predict the hotter the temperature, the quicker the reaction time.
Method
First here is all the equipment that will be needed to conduct both the preliminary and main experiment.
* 5 beakers of water increasing in concentration by 10ml each time,
* 5 beakers with 5ml of Hydrochloric Acid,
* 5 beakers of Sodium Thiosulphate decreasing in concentration by 10ml each time,
* A stop watch,
* A thermometer,
* Goggles,
* Bunsen burner,
* Tripod,
* Gauze,
* Piece of paper with bold cross drawn on,
* An observer.
Preliminary
First we will set up the experiment as shown to the right, with 5 tests in total, each beaker we will add 10 ml water to so the concentration of sodium thiosulphate get less and less each time, then we add the water, hydrochloric acid and the sodium thiosulphate together and start the stop watch,
and timed how long it took the solution to turn so misty that the observer could
no longer see the cross on the paper through the beaker. Then we recorded the results.
Main
The main experiment is similar to the preliminary experiment, but this time we heated the Sodium Thiosulphate to different consecutive temperatures before we added it to the Hydrochloric Acid and Water and observed the reaction.
We put the Sodium Thiosulphate, along with a thermometer, in a beaker and put it on a gauze on a tripod above a Bunsen burner flame and heated it before beginning the reaction observation process and then recorded the results.
Results
We have now completed the preliminary experiments and have recorded our results.
Below is a table of results showing our results from our preliminary experiments investigating the concentration of reactants in the solution.
Amount of Water (ml)
Amount of Hydrochloric Acid (ml)
Amount of Sodium Thiosulphate (ml)
Time (s)
Average (s)
25.55
0
5
50
22.56
24.56
26.57
26.83
0
5
40
29.2
26.27
22.79
36.61
20
5
30
41.89
40.12
41.86
60.05.21
30
5
20
60.11.74
60.09.413
60.11.29
20.10.13
40
5
0
20.21.43
20.31.59
20.43.21
As I can see from these results, they are very accurate and there are no results anomalous enough to affect the investigation, so these are sufficient preliminary results.
Obviously, as seen in this table, the higher the concentration of Sodium Thiosulphate in the solution, (and therefore lower the concentration of water) the faster the reaction took to complete - A better reaction rate.
So in conclusion for our main investigation we will perform the experiments with the solution containing 0ml of water, 5ml of hydrochloric acid and 50 ml of sodium Thiosulphate.
After completing our main experiment, we recorded our results and put them into this table of results.
Temperature (?c)
Time (s)
Average (s)
Error Range (%)
24.57
Room Temp
20.84
22.84
7.89827
(25?c)
23.30
4.23
30
2.24
3.12
6.25816
2.89
6.00
40
8.27
7.28
37.83333
7.57
5.15
50
4.60
4.65
9.21296
4.32
3.59
60
3.24
3.23
25.0871
2.87
2.15
70
2.68
2.47
24.65116
2.59
To check the accuracy of the results, I included the error range for the repeated results.
At Temperature 40?c the results were the least accurate, but this is under 40%, so the results are generally very accurate, and have no need for re-tests. The majority of the error ranges are within a 15% - 25% range, so follow a steady, accurate trend. The results clearly lower in reaction time as the temperature increases, as I predicted. So the best condition for this reaction to perform at is:
* Amount of water
=
0ml
* Amount of hydrochloric acid
=
5ml
* Amount of sodium Thiosulphate
=
50ml
* Temperature of solution
=
70?c
In the graph showing the results for the temperature experiment overleaf, all of the results follow the line of best fit, apart from the result at 25?c, which seems to be slightly anomalous on the graph. But in the results table, due to one minor accident of some sort during the experiment, this result has a slightly longer average reaction time than expected.
The results plotted on the graph are at a strong negative correlation, which shows that the hotter the temperature, the quicker the reaction time. This is because the more the reactants are heated, the more active the particles in the reactant become, which makes the collisions between the particles faster and stronger, causing a faster reaction rate.
I think our results are very accurate, with few anomalous results, and certainly none that greatly affect the investigation.
Possibly next time I would take more care over reading off the temperatures, and be more exact, and the same for measuring the amounts of solutions, so the results would be even more accurate.
I may conduct further experiments that take the temperature above 70°c, because I believe the reaction times may decrease even more as the temperature rises, possibly up to 100°c. the rule for this investigation is that the reaction rate improves as the temperature rises, but this may change at a greater temperature, which could be investigated further.
Graph showing results for Temperature experiment(?c)
