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The effects of change in concentration on the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid.

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  • May 13, 2005
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GCSE SCIENCE COURSEWORK (CHEMISTRY)

PLANNING: Skill Area P

Write down the aim of your Investigation.

To investigate the effects of change in concentration on the rate of reaction between Sodium Thiosulphate and Hydrochloric Acid.

Briefly describe your Preliminary Experiment and include your results. Explain how these results have helped you plan your main experiment (p8b).

An increase in concentration will lead to an increase in the rate of reaction because there will be a greater number of particles per unit/cm3. The particles will be closer together and have greater chance of colliding and therefore reacting. The activation energy barrier is more likely to be overcome when particle with greater energy react therefore collisions are more likely to occur. This can be justified by relating to the Collision theory, which is that '...before we can get a chemical reaction, particles must crash together...' with enough energy. Molecules exceeding the activation energy collide together to initiate the reaction. They must be also correctly orientated in order to successfully collide. This means that the graph drawn up in my analysis will have a negative correlation, because as one variable increases the other one decreases. In this case as concentration increases the time taken for the reaction to occur will decrease. The graph shown below is taken from my preliminary experiment's results and supports this argument.

Volume of

dilute HCl(cm3) Volume of 40g/dm3

Sodium Thiosulphate Volume of

Water(cm3) Time taken for Cross

to disappear(sec)

5 50 0 31

5 40 10 39

5 30 20 52

5 20 30 55

5 10 40 89

List all the apparatus that you now plan to use (diagrams should be included) (P4b).

Based upon my preliminary experiments I decided on using the following apparatus:

x1 stopwatch

x1 thermometer

x2 measuring cylinders

x1 conical flask

x1 beaker

x1 X board

x1 pair of goggles

x1 apron

240cm3 of hydrochloric...