Investigating the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid

Essay by lil_blingy_511High School, 12th gradeA+, April 2004

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Investigating the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid


Aim : We did 4 experiments to find out how the rate of reaction changes with differing concentrations of Sodium Thiosulphate, Hydrochloric Acid and water. As an inert and stable liquid, water was used to alter concentration of Sodium Thiosulphate without changing the end amount of solution. All the atoms in a water molecule have a full outer shell, so they would not react with the other chemicals.

Equipment : Beakers,

Measuring cylinders

Clamp stand and Clamps

Black paper tube

Light probe and Blue box



Total of 30cm3 H 0, 50cm3 Na S O , 12cm3 HCl

Method : We wanted to change the concentration of Sodium Thiosulphate and Hydrochloric Acid, but without changing the overall quantities. To do this, the Sodium Thiosulphate and water were mixed at different ratios, with always a constant amount of acid.

The table below shows the 4 different experiments, and what each solution composed of. The 'Graph' column relates to the graphs taken from the Datalogger for that experiment, which are included at the back of this piece.

Sodium Thio-sulphate (cm3) Water (cm3) Hydrochloric Acid (cm3) Graph number

20 0 3 DPPAS_02

15 5 3 DPPAS_03

10 10 3 DPPAS_04

5 15 3 DPPAS_05

We did not do the experiment in which 0cm3 Sodium Thiosulphate and 20cm3 water were used, as there would have been no reaction. In total, there were always 20cm3 of water and Sodium Thiosulphate, with 3cm3 Hydrochloric Acid, giving a total solution of 23cm3

The black tube was put around and below the beaker to help prevent any unwanted light from entering the light probe, as this would have impaired our results.

The reason we used a Datalogger and light probe instead of the old...