Rates of reaction

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Rates of Reaction

Plan

The aim of this investigation is to find out how the concentration of sodium thiosulphate affects the rate of reaction when reacted with hydrochloric acid. I will use sodium thiosulphate and hydrochloric acid as my two reactants. I will change the concentration of sodium thiosulphate throughout the experiment and time how long it takes for the sulphur to form.

Preliminary Work

Preliminary work helps the people conducting the experiment, by seeing if there are any faults in the experiment that they are doing. It helps by making it easier to plan the main experiment. Also if any problems occur during the preliminary experiments, you can find ways of solving these problems during the main experiment.

From my preliminary work, I found out essential factors that might affect my results. The consistent pattern I found out from my preliminary work is that, ‘the more you increase the concentration of sodium thiosulphate, the quicker the X will disappear under the flask’

For particles to react they must collide and due to their being a reduced amount of particles in a dilute solution there is a lower chance of the reaction taking place.

For my preliminary work I have come to a conclusion not to record any concentration less than four seconds because this reaction happens too quickly for me to record, stopping my readings from being precise and dependable. I have taken an account of what I have just spoken about and from my surveillance in my preliminary work I will not take account of molars from 1.75 and 2.00. I also need to be aware of reactions that will take long.

Equipment

Below is a list of equipment that I will need to carry out this experiment safely.

  • White paper with black cross
  • 2 x 50ml measuring cylinders
  • Sodium thiosulphate of the following molars:
  • 0.25m
  • 0.50m
  • 0.75m
  • 1.00m
  • 1.25m
  • 250ml conical flask
  • Thermometer
  • Two pipettes
  • Stop watch
  • Safety glasses

Chemicals

  • Hydrochloric acid (2M)
  • Distilled Water
  • Sodium thiosulphate (40g/l)

                                                

Method

  1. I gathered all the apparatus and assemble it on the table, which consists of the equipment above. I will put all the equipment to one side to prevent any accidents from occurring. I will then put on my safety glasses.
  2. I will measure 20cm3 of sodium thiosulphate as well as 10cm3 of hydrochloric acid in the measuring cylinders. I will make sure that the two cylinders do not get mixed up by keeping them apart.
  3. I will transfer both reactants into the conical flask one at a time and take the temperature and place the conical flask on the cross.
  4. As soon as the two reactants are poured into the beaker I will start to time for how long it takes the cross on the white paper to disappear. The same person will time and also look directly on top to see if the cross is visible.
  5. When the experiment is over I will drop the solution down the sink straight away and rinse out the flask and cylinders thoroughly to avoid any contamination.
  6. I will note the results down in my science book.
  7. I will repeat these same steps for sodium thiosulphate 0.25m, 0.50m, 0.75m, 1.00m, 1.25m.
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Prediction

My prediction for the rate of reaction is

‘The greater the concentration the faster the rate of reaction’.

I hypothesise this because of the collision theory and my preliminary work. The greater the concentration the more particles there will be, causing a greater chance of a collision therefore, increasing the rate of reaction. Two chemicals react when their particles collide with each other with sufficient energy for the reaction to take place. The two particles will only react if they have enough energy. If the concentration is reduced the reaction rate will also be reduced, this is because there ...

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