Rate of Reaction Between Thiosulphate and Various Concentrations of Hydrochloric Acid

Rate of Reaction Between Thiosulphate and Various Concentrations of Hydrochloric Acid

Aim: The aim of this experiment is to determine the rate of reaction

between thiosulphate(Na2S2O3) and various concentrations of

hydrochloric acid (HCl). The rate of reaction will be measured rather

crudely by seeing how long it takes for the mixture of water and

hydrochloric acid to cloud up the beaker and make a large 'X' under

the beaker in which the solution will be placed unvisable.

Method: In my experiment, I will be using the following apparatus:

o 2 measuring cylinders

o Water

o Beaker

o Hydrochloric acid

o Thiosulphate solution

o Laminated card with a oversized 'X' on it

Diagram:

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Firstly, I will fill the beaker with 50ml of water from the laboratory

taps. The beaker will then placed on the marked paper. Next, the

hydrochloric acid will be added to the Na2SO3 (thiosulphate). At this

point, the stopwatch will be started, and then the time recorded for

the cross to disappear. This will then be done with the concentration

of Na2SO3 increasing in measurements of 10ml each time. I will change

the ratio of water and hydrochloric acid such as 50:0, 40:10, 30:20,

20:30, 10:40, 0:50. This will allow me to determine what ratio is

needed for the reaction to occur quickest (i.e. more acid than water,

the faster the reaction rate).

As I mentioned in the aim, I intend to find out what effect the

concentration of the acid used will have on the rate of reaction

between it and thiosulphate. Therefore, the only variable in this

experiment will be the ratio of the concentration of the hydrochloric

acid and thiosulphate. To vary this, I will dilute the acid with

different amounts of water, changing the ratio of acid to water. Below

are the ratios I will be using:

Acid (ml)

Water (ml)

0

50

(All water)

10

40