An investigation of one factor which affects the rate of reaction between Sodium Thiosulphate solution and hydrochloric acid.

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              Steven Mavrou-St. Edmunds School-61423

An investigation of one factor which affects the rate of

reaction between Sodium Thiosulphate solution and                                  

hydrochloric acid.

     

         Na2 S2 O3 (aq) + 2HCl (aq)  

           =  

       2NaCl(aq) + S(s) + SO2(g) + H2O(l)

       

       Introduction:

       Sodium Thiosulphate solution is a colourless solution and hydrochloric acid is also a

colourless solution. When mixed together and then shaken, the solution gets cloudy until it

becomes a pale yellow colour and you cant see through the solution.

       In this assessment I have been asked to investigate one factor which affects the rate

of reaction between Sodium Thiosulphate solution and Hydrochloric acid. I will do this by

putting a cross underneath my beaker and time how long it takes until I cannot see through

the mixed solution.

       In my investigation I will use my knowledge on the theories of collision and kinetic. I

will also use my knowledge on Activation energy and heat energy.

       

       Collision theory

       It is the theory used to predict the rates of chemical reactions, particularly for gases.

The collision theory is based on the assumption that for a reaction to occur it is necessary

for the reacting atoms or molecules to come together or collide with one another. Not all

collisions bring about chemical change. A collision will be effective in producing chemical

change only if the atoms brought together possess a certain minimum value of internal

energy, equal to the activation energy of the reaction. Furthermore, the colliding species

must be oriented in a manner favourable to the necessary rearrangement of atoms and

electrons, according to the collision theory, the rate at which a chemical reaction proceeds

is equal to the frequency of effective collisions.

       

       

       

       

       Activation energy

       In chemistry, the minimum amount of energy that is required to activate atoms or

molecules to a condition in which they can undergo chemical transformation or physical

transport. You need to break bonds first and then the collisions have to be hard enough.

Not all collisions are successful. They have to have enough energy to break bonds. The

amount of energy they need to get over is called the activation energy.

       

       Energy

       Every chemical change involves a transfer in energy. Chemical energy is stored in

molecules by the bonds between atoms. Bonds are formed or broken when a chemical

reaction occur, resulting in the taking in or release of heat energy. Changing the conditions ,

for example, raising the temperature will affect the stability of these compounds.  

       

       Fair Tests

       In my experiment I will have to control many factors which may affect the

experiment. Throughout my investigation I will only change the concentration of sodium

thiosulphate. While doing this I will have to keep every other factor the same.

I will have to keep the concentration of the hydrochloric acid the same, otherwise if I vary

the concentration it will increase the number of collisions therefore will increase the number

of successful collisions and this will affect my readings dramatically. I will keep it the same

by having the same amount of hydrochloric acid throughout my investigation, which I can

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ensure by using measuring apparatus.

I will have to keep the temperature constant for all my experiments. If I do not, the

temperature will cause more collisions because all the particles will be moving faster and

hitting each other which will break more bonds. I will control the temperature by measuring

it using a thermometer in the solution. If I had the equipment I would use a water bath but

there is not enough equipment available for every student.

I will have to keep the amount of stirring constant. If I do not it will change ...

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