An Investigation Of The Reaction Between Hcl And Sodium Thiosulphate

Science Investigation

Srategy

I am ivestigating the reaction of sodium thiosulphate and hydroclohric acid.

sodium thiosulphate(aq) + Hydroclohric Acid (aq) --> Sodium cloride (aq) + Sulphur Dioxide (g) + Water (l) + Suplhur (s)

Na(2)S(2)O(3) + 2 HCl --> 2NaCl + SO(2) + H(2)O + S

The finished reaction of the 2 clear liquids is cloudy.I will use this change from clear to cloudy as an indicator as to when the reaction is finished.

By using this change , i can see the effect of changing other factors has upon the rate of reaction.I will be sure to only change one factor at a time

(as far as possible) because otherwise i will not know which factors are influencing the rate of the reaction.

I have decided that changing the (molar) Concentration of the hydroclohric acid is the factor im going to investigate.

My Hypothesis is that as i decrease the concentration of the hydroclohric acid, the rate of reaction will also decrease.I Belive This Because Chemical

Reactions occur using the Collision theory (proposed by Max Trautz and William Lewis in 1916 and 1918) .This theory states that the reactant particles

must collide, but only a certain fraction of the total collisions (the effective collisions, the molecules that have sufficient energy at the moment

of impact to break the existing bonds and form new bonds, Called activation energy) cause the transformation of reactant molecules into product.With

a higher concentration of HCl there are more molecules to collide , giving more chances for them to break bonds.

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Equipment

3 Burettes ( One for water , One for HCl and the other for sodium thosulphate)

Distilled Water

Beaker(s)

HCl (1 Molar)

Sodium Thosulphate (0.25 molar)

Data Logger

Timer

I have elected to use burettes beacuse these will allow for more accurate measurement

( to within 1/10 ml) And I will be using one for each substance

so that there is no cross contamination between the chemicals.I am using a data logger

to show hom much light can penetrate the solution becuase it

much more reliable and more accurate than human vision.

Note : before the experiment can be timed, a value must be set to represent the value at which the timer shoudl be stopped.To set this value , I will

do the experiment at 1 molar but not