The Factors Controlling the Rate of the Sodium Thiosulphate and Acid Reaction

2577 Words Jun 25th, 2018 11 Pages
The Factors Controlling the Rate of the Sodium Thiosulphate and Acid Reaction


I am investigating the factors controlling the rate of thiosulphate / acid reaction. The reaction that will be taking place will follow the rate at which sulphur is formed in the reaction of sodium thiosulphate with dilute hydrochloric acid. In the experiment the sulphur will appear as an extremely fine precipitate. This will slowly be followed by a milky appearance in the reaction mixture in the conical flask. As the amount of the sulphur in the mixture increases, the precipitate will become milkier. Gradually the liquid will become more and more opaque. To investigate the rate of the reaction, we will use
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It is a reduction to one quarter of the rate at the beginning.


No. of particles

with given KE


[IMAGE][IMAGE] Hotter substance

[IMAGE][IMAGE] Higher temperature

[IMAGE][IMAGE] Activation energy

[IMAGE][IMAGE] Energy Min K.E for reaction

No of molecules with K.E> The minimum energy needed to react is directly proportional to the shaded area

By looking at the graph one can say that by looking at the shape of the curve the area surely must increase with increased temperature.

The Preliminary Experiment

The aim of the preliminary experiment was to find out suitable concentrations of thiosulphate one should put in to the reaction. I did not want to end up doing the experiment without knowing how long it will take and which concentrations would be suitable.


Ø Apparatus: Conical flask, burette, stopwatch, a cross on a piece of paper, a thermometer and safety glasses.

Ø Safety procedures: One must wear safety glasses at all times because there are dangerous chemicals in the experiment. One should also stand up when doing the experiment so if the flask falls off the bench you do not get hurt.

Ø Firstly I chose three concentration levels for the experiment. These are shown in the table below.

Volume of thiosulphate

(cm )

Volume of H2O

(cm )

Volume of HCL (cm )


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