Thiosulphate Acid Chloride Dioxide
Na S O + 2HCl S + 2NaCl + SO + H O
Apparatus:
Sodium Thiosulphate for the reaction
Hydrochloric Acid for the reaction
Conical Flask to pour in the two solutions. It’s where the reaction takes place.
10cm glass measuring cylinder because it’s more accurate for measuring 5cm than a 100cm measuring cylinder would be. And with glass it will more accurate than plastic.
100cm glass measuring cylinder because it’s more suitable to measure 40cm of a solution. And with glass it will more accurate than plastic.
Stop watch to time the reaction for each concentration.
Scrap paper with large cross drawn on it to see when reaction has fully taken place.
Sodium Hydrogen Carbonate and Hydrochloric Acid (in a bowl to neutralise the reactants)
- Measure 5cm of Hydrochloric Acid into a 10cm measuring cylinder.
- Measure 40cm of Sodium Thiosulphate into a 100cm glass measuring cylinder.
- (The 40cm cylinder is used because if a 25cm was used there would be a possibility of there being two slight errors with having to measure the solution volume out twice whereas with a 100cm measuring cylinder there is only risk of one error, therefore makes the volume more accurate.)
- Pour the 40cm of Sodium Thiosulphate into a conical flask.
- Draw a clear cross onto a piece of plain white paper large enough to be visible through the conical flask. The same cross must be used for each and every test carried out to keep the whole experiment as fair as possible.
- Place the conical flask on top of the piece of paper.
- Pour the 5cm Hydrochloric Acid into the conical flask along with the Sodium Sulphate.
- Swirl the solution in the conical flask once and then trigger a timer.
- Time with the stop watch until the reaction in the flask has prevented you to see the cross underneath it as it turns a yellow colour.
- The time should be recorded in a table.
- The test described here contained the more concentrated solution. The same test must be carried out 3 times for each different solution.
- The concentration for each test needed to be carried out are:
1) 40g/litre = 40cm + no water
2) 30g/litre = 30cm + 10cm water
3) 20g/litre = 20cm + 20cm water
4) 10g/litre = 10cm + 30cm water
5) 5g/litre = 5cm + 35cm water
To work out the number of moles for each one the following formula must be used:
Moles = Mass
Molecular Formula
Therefore:
Na S O
1) 23 + 23 + 32 + 32 + 16 + 16 + 16 = 158
Moles = 40 = 0.2351
158
The same happens for each of the concentration therefore:
2) Moles = 30 = 0.1899
158
3) Moles = 20 = 0.1266
158
4) Moles = 10 = 0.0632
158
5) Moles = 5 = 0.0316
158
3 tests need to be carried out for each of these solutions.
Preliminary Work:
The preliminary work involved 2 experiments which involved concentration of a solution and temperature change. The first was titled, ‘the effect of concentration on the rate’. In this experiment a bowl is filled with water, which contains a beehive dish with a measuring cylinder on the top of it. There is a delivery tube from this connected to a bung which is in the top of a conical flask. The flask contains a specific acid concentration with marble chips. This concentration changes each time the experiment is carried out. The gas given off the reaction between the acid and the chips is delivered to the measuring cylinder and then measured. There should be 3 test for each different concentration used. Water is used to dilute the solution so that the concentration decreases, but the volume is always the same in every test. From this experiment the conclusion was that as the concentration of the acid decreases, the time taken to collect 50cm of Carbon Dioxide from the reaction, increases. This means the rate of reaction decreases as the concentration is less. This is because there are more particles to collide at higher concentrations so these are more successful collisions.
Another experiment carried out was the ‘effect of temperature on the rate of reaction’. This is when 50cm Sodium Thiosulphate is poured into a conical flask which is placed above a clear cross drawn on a piece of paper. 5cm of Hydrochloric Acid is added after the Thiosulphate has been heated to a sensible temperature. The time taken for the cross to disappear is then recorded. This test should be carried out 3 times and then the temperature should be changed so that the molecules are moving at different rates. In conclusion to this experiment, as the temperature of the liquid increases the time taken for the reaction to take place decreases. This means the rate of reaction increases and becomes faster. This is because the particles are now colliding at a faster speed on temperature increasing in the liquid makes the particles vibrate vigorously. The particles have enough energy to collide successfully as they have more energy than the activation energy.
These experiments help with my prediction because they both show that the more molecules there are the more reaction there is. This is due to both the quantity and the temperature at which they are. If there are fewer molecules there will be a decrease in the rate of reaction and the less heat there is to help the molecules move the less chance there is of them all colliding.
Results and range of results:
TIME TAKEN minute.second.tenth
Bibliography:
Chemistry for you Lawrie Ryan 1996
Observation:
Method:
There were no major changes in the experiment. Everything went forward as originally planned in the method.
Results:
TIME TAKEN minute.second.tenth
The concentration calculation to get the units into g/per litre is:
Volume of Sodium Thiosulphate x Initial Concentration
Total Volume (g/per litre)
40 x 40 = 40
40
30 x 40 = 30
40
20 x 40 = 20
40
10 x 40 = 10
40
5 x 40 = 5
40
The rate of reaction is calculated by dividing the average by 1.
I.E. 1 = 0.0272
36.70
Conclusion:
The results show that the higher the concentration the higher the rate of reaction there is. This is shown in the table of results. The average shows that the less the concentration the longer the time for there to be a full reaction. The results in the rate column decrease going down the table. The concentration in g/per litre also decreases as you go down the table. Here is an example:
Therefore the less the concentration the less chance there is of a reaction occurring quickly.
The first graph showing the length of time it took for a reaction to occur in different concentrations of a solution, gives a trend. The more concentrated the solution the shorter time it took for a full reaction to occur, which blocked the view of the cross underneath the conical flask. This is shown by a clear curve.
The second graph shows the rate of reaction for the different concentrations. Shown by a line of best fit the higher the concentration the bigger the rate of reaction was. This shows that it takes longer for a solution of less concentration to react properly. The results back up my prediction because as stated ‘I predict that as the concentration of the solution decreases the rate of reaction will decrease too.’ It shows that it is true that the length of time for the cross to disappear will increase as the concentration decreases. This is because more molecules are present in a higher concentration and therefore there was more of a chance of the particles colliding with each other. The more particles there were the more chance there was of having more energy than the activation energy, this is proved in this experiment. The solution proved to be very crowded and it didn’t increase the speed at which they collide only the temperature change could do that.
Evaluation:
This was as much a fair test as possible using the same equipment all of the way through the experiment. The solutions used were constant all the way through also. The cross used to carry out the tests was the same one all of the way through and the solutions were measured out as accurately as they could have been, using the measuring cylinders provided. The measurements of the solutions didn’t change apart from the ones where the concentration had to be changed, which was the point in the whole experiment.
The procedure was seemingly easy to follow through. It was a simple experiment which told us what the effect of concentration was in a reaction. There were no obstructions whilst actually carrying out the experiment. The procedure proved to give good results. Most of the results were very similar when using the same solutions. There were only a couple of results that were more than a few seconds out to the other tests carried out. The results achieved were very reliable. This is because all of the tests carried out with the same concentration were carried out at the same time therefore the tests were carried out in a short time of each other. Because of this these results are very trustworthy. The procedure carried out was very helpful to investigate my aim. It told us the concentration of a solution determines an effect of a reaction as the investigation was to ‘investigate the effect of concentration on the rate of a reaction.’ Therefore my aim was fulfilled. There was nothing in this experiment that proved to be difficult or a challenge. The results were fairly accurate as they were to 2 decimal places. If they were much more accurate it would become fairly complicated as the unit was seconds. There was one anomaly in this experiment being this result:
This could have been for many reasons. The main one being that the measurements for this test weren’t as accurate as the other 2 taken and therefore the result has become quite different to the others. The measurement could have been wrong for any of the solutions, that is the water, Hydrochloric Acid and the Sodium Thiosulphate.
This experiment could have been improved through many things. Computerised equipment could have been used to improve the accuracy of the measurements as it is an awesome lot more accurate than the naked eye. The solutions could have been timed more often, so instead of 3 times maybe 10 and that way the average would be a lot more accurate. Another experiment that could be carried out to measure the rate of reaction would be the ‘volume of gas given off.’ For this, a conical flask needs to contain a sensible amount of dilute hydrochloric acid. There should be a bung in the top containing a tube which leads to a syringe. Marble chips should be put into the flask, and the bung put straight back in again. Collect the gas given off from the marble chips in the syringe and when 100cm has been collected stop timing how long it took. This should be carried out a sufficient number of times to get an accurate reading.
