chemistry coursework rate of reaction

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 The effect of changing the concentration on the rate of a reaction

Research

There are 4 ways to alter a reaction:

  • Surface area-

If you break 1 chunk of a solid into smaller particles it will have a larger surface area, this larger surface area will allow more collisions to occur; therefore speeding up the reaction.

  • Concentration

In order for any reaction to happen, those particles must first collide. This is true whether both particles are in solution, or whether one is in solution and the other a solid. If the concentration is higher, the chances of collision are greater.

  • Temperature

When a reaction is heated the atoms are given more energy, therefore move faster. This will make more collisions speeding up the reaction

  • Catalyst

A catalyst provides an alternative route with a lower activation energy. Using less energy means there will more collisions and quicker.

Introduction

By looking at the variables from my research I have come to the conclusion that I cannot use a catalyst; as it would be too difficult to find the correct one, and surface area because they are both liquids. So I was left with concentration and temperature. I decided to use concentration as I believe it will be, overall, an easier experiment to do.

I am going to see how concentration affects the rate of the reaction. In this experiment solution A (a mixture of water and sodium thiosulphate) reacts with Hydrochloric acid to produce sodium chloride, water, sulphur dioxide and sulphur. The Sulphur that is produced during the reaction produces a yellow precipitate of sulphur. I am going to use different concentrations and see how it affects the time it takes for the reaction to complete.

The equation for this reaction is:

Na2S2O3(aq) + 2HCL(aq) = 2NaCl(aq) = H2O(l) = SO2(aq) + S(s)

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Sodium        + Hydrochloric = Sodium   + Sulphur + Sulphur

thiosulphate    acid                   chloride    dioxide          

Prediction

I Think that the higher the concentration, the higher the rate, (the shorter the time for the solution to produce a precipitate of sulphur) the faster the reaction will go. At a higher concentration there is larger proportion of Sodium Thiosulphate molecules to the same amount of space and they are more likely to collide with the Hydrochloric acid, speeding up the reaction as there ...

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