In a chemical reaction, the reactants collide with each other.
Pressure
High pressure
Low pressure
Not many collisions
Marble in dilute hydrochloric acid
1 Large marble cube Marble cube split into 6 pieces
In the experiment I carry out, I will change the concentration and see if different concentrations make a difference.
The equation of this experiment is:
Na2 S2 O3 + 2HCl 2NaCl + SO2 + S + H2O
Sodium thiosulphate + hydrochloric acid sodium chloride + sulphur dioxide + sulphur + water
Health and Safety:
Before the experiment is carried out I must have a safe environment, in order to prevent accidents.
- Wear goggles before touching any chemicals or equipment.
- After the experiment wash your hands thoroughly with liquid.
When sodium thiosulphate and hydrochloric acid react, a gas called sulphur dioxide is released. Sulphur dioxide turns into sulphuric acid when it comes in contact with the moisture in your respiratory system. The sulphuric acid can burn away layers on your throat, which could cause a sore throat.
Apparatus:
- Measuring Cylinder ( 50cm³ and 10cm³)
- Solution of Sodium Thiosulphate
- Solution of Hydrochloric Acid
- Sheet of paper with an ‘X’ marked on it.
Preliminary Work:
When I done my preliminary work I recorded the results on a table. I did the preliminary work, so I can choose the concentration and when to vary it in my experiment.
I got these results by following a method that the teacher gave us.
Preliminary Method:
- Fill up 5cm³ of HCL in a measuring cylinder and 25cm³ of sodium thiosulphate in another measuring cylinder.
- Empty the sodium thiosulphate in the conical flask and then place the conical flask over the piece of paper with the “X” marked on it.
The next few steps we had to do fairly quickly.
- Add the hydrochloric acid to the conical flask, as soon as the two solutions come in contact with each other, start the stop watch.
- Gently swirl the conical flask so the two solutions can react, while doing this be careful not to breathe in the products produced by this reaction.
- When the contents of the conical flask starts to go cloudy, look into the conical flask from above and wait for the “X” to disappear.
- When the “X” has disappeared stop the stop watch and record the time on the results table.
Repeat this procedure 3 times with the same measurements and then repeat the same experiment using the measurement provided in the results table. The method must be repeated 3 times for each set of measurements, in order to work out the average time when the results need to be recorded onto a graph.
Method:
The method I used for the preliminary work is the same as the one I used in the real experiment. I used the same method as nothing needed to be changed, not even the concentrations of the solutions.
- Fill up 5cm³ of HCl in a measuring cylinder and 25cm³ of sodium thiosulphate in another measuring cylinder.
- Empty the sodium thiosulphate in the conical flask and then place the conical flask over the piece of paper with the “X” marked on it.
The next few steps we had to do fairly quickly.
- Add the hydrochloric acid to the conical flask, as soon as the two solutions come in contact with each other, start the stop watch.
- Gently swirl the conical flask so the two solutions can react, while doing this be careful not to breathe in the products produced by this reaction.
- When the contents of the conical flask starts to go cloudy, look into the conical flask from above and wait for the “X” to disappear.
- When the “X” has disappeared stop the stop watch and record the time on the results table.
Repeat this procedure 3 times with the same measurements and then repeat the same experiment using the measurement provided in the results table. The method must be repeated 3 times for each set of measurements, in order to work out the average time when the results need to be recorded onto a graph.
Results:
These results were produced by using the method above.
Graphs are attached at the end of this piece of coursework.
Conclusion:
In my hypothesis I wrote “I hypothesis’ that the higher the concentration of sodium thiosulphate, the faster the rate of reaction.”
I believe the results I have obtained prove my prediction. My results clearly state that my predictions are correct and I believe the collision theory is correct. My results showed that the higher the concentration of sodium thiosulphate the faster the rate of reaction. In the experiment there were a few anomalies I came across. Not all the results were on the line of best fit. They could have occurred by me using contaminated equipment. I did wash all the equipment thoroughly, but I did not have sufficient cleaning materials at hand. Also the anomalies could have occurred because there was too much or too little of a chemical. Again I tried my best to keep the measurements accurate. Some of the bottles that contained the chemicals could have been contaminated, but there was no way of telling if they were or not, so I carried on with my experiment assuming they were not. I noticed the anomalies where the graph was drawn up. I could avoid these anomalies by decontaminating all the equipment I used, make sure the chemicals I use are fresh and also make my measuring of the chemicals used, more accurately.
Evaluation:
I think the experiment was fair, apart from a few anomalies. I could avoid these anomalies by decontaminating all the equipment I use, make sure the chemicals I use are fresh and also make my measuring of the chemicals used more accurate. I could extend the experiment by testing temperature instead of concentration and then compare the results. My repeats are seconds out apart from the last row on the table. I think that the results are as accurate I will be able to get them. The measuring equipment I used could be at fault, I don’t the equipment was that accurate. But in a school laboratory it is difficult to get the results you expected.
By Veenesh Halai
