I am investigating how the effect of concentration has on the rate of reaction between hydrochloric acid and sodium thiosulphate

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Investigation on the Effect of Concentration on the Rate of Reaction

Between Hydrochloric Acid and Sodium Thiosulphate

Introduction

I am investigating the effect on the rate of reaction between hydrochloric acid and sodium thiosulphate when the concentration of the hydrochloric acid is varied. The end of the reaction will be observed as the solution will turn cloudy yellow due to the sulphur precipitate produced.

Sodium Thiosulphate’s physical properties range from being a solid as translucent crystals or white crystalline powder but can also be a liquid which is what we are going to use for this experiment. Its melting point is 48 C. It is an irritant so when used ALWAYS wear safety goggles. The formula for Sodium Thiosulphate is Na2S2O3 5H2O.

Hydrochloric Acid’s physical property depends on whether it is concentrated or not. I fit is concentrated the substance is colourless to light yellow liquid while if it is diluted it is a colourless liquid. Its boiling point is 109 C. It is corrosive and toxic so when being used ALWAYS wear protective clothing and use in a well ventilated area. The formula for Hydrochloric Acid is HCl.

A black cross will be drawn onto a piece of paper and place underneath the conical flask which is where the reaction will take place. The time taken for the black cross to be obscured by the sulphur precipitate will be noted and the rate of reaction calculated using the formula 1/time.

Wikipedia Encyclopedia defines rate of reaction as:

‘The amount (in moles or mass units) per unit time per

 unit volume that is formed or removed’

The Oxford GCSE Chemistry Book defines rate of reaction as:

‘The speed at which the reaction between two or more substances takes place.’

For a reaction to take place the substance particles must collide. If they collide with enough energy they will react. The minimum amount of kinetic energy that the two particles need to produce a reaction is called the activation energy. If the particles are colliding more the rate of reaction is higher. A solution of acid with a lower concentration has less acid particles and more water particles. So when more acid is mixed with less water the concentration will get stronger. Increasing the concentration of the solution leads to a greater frequency of collisions so the rate of reaction increases.

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An experiment was previously done to determine the effect of concentration on the rate of reaction using hydrochloric acid and a magnesium ribbon. The results showed that at a higher concentration the rate of reaction between hydrochloric acid and magnesium was higher.

The reaction that will be investigated is between hydrochloric acid and sodium thiosulphate.

The reaction as shown in the equation below:

           

Preliminary Results

A preliminary experiment was done to find out what volume and concentration should then be used to get the ...

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