How does the concentration of Sodium Thiosulphate solution affect the rate of its reaction with Hydrochloric acid?

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How does the concentration of Sodium Thiosulphate solution affect the rate of its reaction with Hydrochloric acid?

Prediction

I predict that the higher the concentration of Sodium Thiosulphate solution the quicker the rate of reaction with Hydrochloric acid will be. I think this because the collision theory says that a higher concentration means a larger number of particles in a given volume. If there are more particles, there will be more collisions. More collisions mean a larger number of successful collisions. Therefore the reaction rate will increase.

              low concentration                                    high concentration

Fair test

To make my experiment a fair test I will keep the following variables the same:

  • The temperature of the Sodium Thiosulphate
  • The total volume of all the liquids when added together
  • The amount of Hydrochloric acid
  • The same cross
  • Always measure the level of liquid at the meniscus
  • Use the same person to measure out the liquid
  • Make sure the stopwatch is started when the Hydrochloric acid first hits the Sodium Thiosulphate solution
  • Use the same person to start the stopwatch

It is important to keep all the variables the same accept the volume of Thiosulphate solution and water because they could alter the experiment and it would not prove that the concentration increases the rate of the reaction.

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Equipment

  • Measuring cylinder
  • Conical flask
  • Stop clock
  • Thermometer
  • Cross on piece of paper
  • Small beaker
  • Medium beaker
  • Large beaker
  • Safety glasses

Method  

I am going to measure out 50cm³ of Sodium Thiosulphate solution using a measuring cylinder, pour it into a conical flask and record the temperature using a thermometer. Then I will measure out using a different measuring cylinder 10cm³ of Hydrochloric acid. I will then place the conical flask containing ...

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