The rate of reaction between Sulphur Thiosulphate and Hydrochloric Acid.

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Rate Of Reaction

Planning

Aim:

To investigate the rate of reaction between Sulphur Thiosulphate and Hydrochloric Acid.

This experiment is primarily based on chemical reactions and what affects the rate of these reactions.

  To grasp the idea of the experiment, one must first understand the fundamental knowledge behind chemical reactions.

  The features of a chemical reaction are summarised below:

  • One or more new substances are produced. In many cases an observable change is apparent, for example a colour change or a gas is produced.
  • An apparent change in mass may also occur. The change is usually due to gas being given off.
  • An energy change is almost always involved. In most cases energy is released and the surroundings become warmer. In some cases energy is absorbed from the surroundings and so the surroundings become cooler.

For a chemical reaction to occur, the reacting particles (atoms, molecules and ions) must collide. There must be enough energy involved in the collision to break the chemical bonds in the reacting molecules. If the energy transfer is not large enough the particles will just bounce off one another. A collision with enough energy to result in a chemical reaction is referred to as an 'effective collision'. This approach is called the collision theory.

Particles must

 Collide with enough energy to

Make an effective collision.

 

Some chemical reactions occur extremely quickly, for example, the explosive reaction between petrol and oxygen in a car engine is over a fraction of a second.

  Other chemical reactions are much slower. It usually takes days before there is an obvious sign of a reaction when iron rusts. The reason why reactions occur at different times is because they have different activation energies. The activation energy is the minimum amount of energy required in a collision for a reaction to occur.

A quick reaction takes place in a short time. It is said to have a high rate of reaction. As the time taken for a reaction to be completed increases, the rate of the reaction decreases:

        

        Rate = 1            

                    Time                                

Fair Test:

  In order for my findings to be valid the experiment must be a fair one.  

  The temperature:

This will be kept at room temperature best I can therefore the experiment will not be carried out near a wind where the temperature may vary. Also, by increasing the temperature of a solution, the higher the rate of reaction will be.

   The volume of Sodium Thiosulphate:

This will be kept the same at 10cm³. This is because if there is too much of the solution the rate of reaction will be quicker and the sodium Thiosulphate particles will collide with each other.

  The same beaker:

This must be used throughout the experiment in case another has a slightly larger surface area or has been contaminated.

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   I will use the same standard each time for judging when the X has disappeared. The same person will be used to judge whether or not they feel the X at the bottom of the beaker has disappeared, as different people have different judgements.

I will make sure that the measuring instruments used to measure the Hydrochloric acid and Sodium Thiosulphate will not be mixed up.

   To keep my investigation as fair as possible, I must change only one factor at a time. The factor I will be changing is the concentration of the hydrochloric acid. The ...

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