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Chem coursework - Sodium Thiosulphate and Hydrochloric Acid Watch

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    Im doing the thio + HCl reaction for my GCSE chem coursework.
    Im a bit stuck on why its important that the reactants are always added in the same order? i.e. thio after HCl or vice versa

    thank you
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    In general, it's not important which order they are added for the reaction to actually happen. The reaction will happen either way around:

    HCl(aq)    +   Na_2S_2O_3(aq)  \rightarrow            NaCl(aq)       +     SO_2(g)       +       S(s)  +  H_2O(l)

    But if you are doing a titration several times with different concentrations, it is important that the thing you add from the burette (usually the acid) is always done the same way so your results can be compared properly. Usually you are measuring the amount of acid required to turn the solution cloudy and obscure the cross under the flask.

    Hope this helps
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    Like Plato's Trousers said it shouldn't matter which order you add them in.

    However when i did it i always added the hydrochloric acid to the sodium thiosulophate because it meant i only had to clean out the beaker the reaction's taking place in before remaking the sodium thiosulphate solution.
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    Hi

    Im doing this experiment for my A2 OCR B Salters Individual Investigation.

    Is it true that this is a GCSE coursework, therefore I wont get good marks for it at A2?

    Also, is there a possible catalyst for the Sodium Thiosulphate and Hydrochloric Acid reaction?
 
 
 
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