How does the concentration of sodium thiosulphate acid affect the rate of reaction?

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How does the concentration of sodium thiosulphate acid affect the rate of reaction?


In this investigation my aim is to find out how the rate of reaction between Sodium thiosulphate and Hydrochloric acid is affected by the concentration.


The purpose of this investigation is to understand the effects of changing concentrations of variables have on the rate of reaction.

The reaction is going to be between two chemicals, Sodium thiosulphate solution and hydrochloric acid dilute.

The equation below shows how they react.

sodium thiosulphate + hydrochloric acid  sodium chloride + sulphur + sulphur dioxide + water

Na2S2O3(aq) + 2HCl(aq)  2NaCl(aq) + S(s) + SO2(g) + H2O(l)


The collision theory sets to clarify how chemical reactions take place and where the rate of reaction vary. Reactant particles must collide for a reaction to occur. Only a percentage of collisions cause chemical change; these are called successful collisions. These successful collisions have sufficient energy at the moment of impact to split existing bonds and forms new ones. Therefore increasing the concentration of reactants as well as raising temperatures result in more collision and consequently more successful collisions, thus increasing the rate of reaction.


Input-The variable in this experiment is the concentration of hydrochloric acid. I tested five different molar strengths  of hydrochloric acid by adding it to a50ml of Sodium thiosulphate.

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Output-The time of reaction is also expected to vary due to changes in concentration

Controlled-These are unrelated factors, which could possibly effect the results. They are kept constant to minimize their effects on the outcome.

Fair testing:

An test must be fair to produce accurate results. To make this experiment a fair test a number of factors must be controlled.

Firstly the volume of hydrochloric acid and sodium thiosulphate must always be the same .An failure to do so will make it impossible to compare the rate of reaction with repeated experiments.

In this test we are attempting to ...

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