Rates of Reaction - The concentration of hydrochloric acid and the rate of reaction with sodium theosulphate

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Rate of Reaction

After doing my pilot run, i think that my method and apparatus used should be mostly the same:

Apparatus - 1 conical flask

- 1 lamenated 'x'
- 3 test tubes
- 1 thermometer
- 1 stop watch
- 3 pipettes


1. Measure 10ml of 0.2mol/dm3 or 0.2moldm-3 sodium thiosulphate 2. Pour it into the conical flask

3. Add 40ml of distilled water for dillution.

4. Then add 5cm3 of dilute hydrochloric acid of concentration
2mol/dm3 at room temperature

5. Record the temperature of the mixture. Stir mixture gently.

6. Stir mixture gently

7. Start time when all is stirred and when the conical flask is over the 'X' paper.

8. Once the cross is completely out of sight due to the reactionof the sodium thiosulphate and hydrochloric acid and then record the time.

9. I willl then repeat this with different measurements of sodium thiosulphate and water.

Changes I have made and why

- I am not going to be using a burette because after finishing my pilot run, i realised that i was gradually getting more and more behind schedule and I wouldn;t have enough time to complete my obtaining evidence if I were to carry on using it.

Fair test

To make sure it was a fair test. i had to constantly keep cleaning and washing the equipmentas any remaining substances can cause major differences in the results. And we had to try ansd hope that the room temperature will remain constant during the course of my experiment.
Also we always have to keep the volume of concentrstion the same -

number and range of experiments

- If I have enough time, I would like to try around nine different concentrations of sodium thiosulphate with water. I am going to try hte following volumes of sodium thiosulphate: 10ml, 15ml, 20ml,
25ml, 30ml,35ml, 40ml,45ml and 50ml.

- I have chosen a range of 40ml as I think this is enough to truly experience the various actions of sodium thiosulphate reacting with hydrochloric acid.

- If any of my results seem somewhat innaccurate or faulty, I will try my best to redo them.


- Make sure to tie hair back.
- Wear a lab coat.
- Wear safety glasses or goggles.
- Wash hand in between each experimewnt and after anmd before eating.
- Open windows so the smell isn't too overwhelming


To make my experiment a fair test, we must always have the same volume of solutions, 55ml.

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