The Reaction Between Hydrochloric Acid and Sodium Thiosulphate

The Reaction Between Hydrochloric Acid and Sodium Thiosulphate

Introduction

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I am investigating how different concentrations of thiosulphate and

distilled water in ratio to 10cm³ of hydrochloric acid affect the rate

of reaction. I will also investigate if there will be a change in

temperature after the reaction has occurred. I will know when the

reaction is taking place as the solution turns from clear to opaque.

The reaction that takes place is as follows: -

Sodium + Hydrochloric à Sulphur + Sulphur + Sodium + Water

Thiosulphate acid dioxide chloride

Na S O + 2HCl à S + SO + 2NaCl + H O

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The reaction will have finished when the solution has turned

completely opaque and it is visible that the solution is not turning

increasingly more so. At atomic level, at this point all of the

particles in the solution will have stopped colliding.

My prediction

I predict that as the concentration of distilled water to sodium

thiosulphate increases, the rate of reaction will take longer as the

distilled water is making the solution weaker. This is due to the fact

that there will be less fruitful collisions between sodium

thiosulphate and the hydrochloric acid. This can be easier described

by using the following diagrams: -

Here there are many successful collisions between the sodium

thiosulphate and the hydrochloric acid because there is a large volume

of sodium thiosulphate in ration the volume of water, meaning that the

water cannot dilute the solution to a great enough extent.

Here there is no where near as many successful collisions as seen

previously. This is because there is a larger volume of water in

ration to the volume of sodium thiosulphate, meaning that there will

not be as many sodium thiosulphate molecules that would be able to

collide successfully.

Due to this collision theory, the higher the concentration of sodium

thiosulphate, the quicker the rate of reaction because there will be

more successful collisions happening in a shorter space of time.