Rate of Reaction between Sodium Thiosulphate and Dilute Hydrochloric acid

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Chemistry Coursework

The Rate of Reaction between Sodium Thiosulphate and Dilute Hydrochloric Acid.



The word equation for this experiment is:

    Sodium      + Hydrochloric                      Sodium   +  Sulphur + Sulphur + Water

Thiosulphate          Acid                              Chloride      Dioxide

I was told the word equation by my teacher but to find the balanced equation I searched the internet.  It is as follows:

Na S O  +  2HCl               2NaCl  +  SO   +  H O  +  S


I will be investigating the effect of the two reactants; ‘Sodium Thiosulphate’ and ‘Dilute Hydrochloric Acid’ when the amounts of these are varied.  The investigation is to observe the speed of these reactants, and to do this we see how long the cross is clear until the sulphur covers it.


Precautions that will have to be taken in order to keep myself and others around me safe are as follows:

  • Wear goggles at all times to keep any chemicals from entering my eyes-especially as I am working with chemicals such as hydrochloric acid which can be harmful.
  • When I am finished with a chemical I must close it to avoid any accidents/spillages.
  •  Nobody should be running in the lab because accidents are caused that way.
  • I will need to be focused on the task at hand so no mistakes/accidents occur to me or anyone else.


  1. Conical Flask
  1. Measuring Cylinder (10ml/50ml)
  1. A cross
  1. Stop Clock
  1. Distilled Water
  1. Dilute Hydrochloric Acid (1 molar)
  1. Sodium Thiosulphate
  1. Goggles

Range of Values:-

These values are what I intend to use as part of my experiment in the exact quantities shown above.

Method:-(what I plan to happen)

  1. Firstly, I will gather all my equipment that I need for the experiment.  This will help me as I will be organised and also it will save time during the investigation by not constantly getting up to get things.

  1. Next, I will measure out the distilled water and Sodium Thiosulphate in the 50ml measuring cylinder and the acid in the 10ml cylinder because the amount of acid that I will need to obtain will be a lot less so this way I could be more accurate about it.
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  1. I will pour the water in the conicle flask (which was on top of the cross) and then pour the Sodium Thiosulphate and the acid in at the same time so I can be sure that the reaction starts at that moment.  Then I will start the stop clock.

  1. I will stir it because I think that it will help the reaction move forward quicker.

  1. I will repeat each amount 3 times so I can get an average.  This will help me to see whether my results are reasonable compared to other results that ...

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