Essay about Investigation of Sodium Thiosulphate and Hydrochloric Acid

630 Words 3 Pages
The purpose of this investigation is to record the amount of time taken for a reaction to occur when sodium thiosulphate is mixed with hydrochloric acid.
The equation for this reaction is:
Na2S2O3 + 2HCl → 2NaCl + S + SO2 +H2O

Sodium thiosulphate (Na2S2O3), after reacting with Hydrochloric Acid (HCl) produces yellow sulphur, which is the cause of the solution becoming cloudy.

The amount of time taken for the reaction to occur is known as the reaction rate. The rate of a reaction can be commonly explained by Collision Theory. This theory states that in order for a reaction to occur, the particles of each reactant must collide together, with successful collisions resulting in chemical changes. Activation energy is released when the
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Based on this theory, one can predict that the rate of reaction will decrease as the concentration of the Hydrochloric Acid decreases as well.

In order to perform the experiment, the following Apparatus must be used:
50ml of Na2S2O3 – Sodium Thiosulphate, a reactant
10ml of HCl – Hydrochloric Acid, a reactant
Conical flask – Used to contain the solution during the reaction
Measuring Cylinder – Used to measure the amount of Sodium Thiosulphate used in each experiment
Stop clock – Used to measure the amount of time taken for reaction to take place
Card with cross – Used to identify when the reaction has finished.

The input variable in this experiment is the concentration of the acid. In each progressive experiment, the amount of acid in the pipette will decrease by 2ml, and the difference to the original amount of acid will be replaced with water. The output variable will be the time taken for the reaction to take place, and should change according to the input variable.
The controlled variable will be the Sodium Thiosulphate. The amount used must remain the same throughout the whole experiment. A control variable is a factor that is kept constant so as to reduce the effect it has on the output variable.

1.50ml of Sodium Thiosulphate will be poured out into a measuring cylinder to be placed into the conical flask. The card with the cross should already placed beneath.
2.For the first

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