Chemistry Concentration effects rate of reaction

Authors Avatar

How does concentration affect the rate of a reation

In this experiment I will have to look at how concentration affects the rate of reaction.   I will have to decide which concentrations to change, and the reaction that I will be performing.

Prediction

The reaction I have chosen is:

Sodium         +  Hydrochloric ⇒ Sulphur + Sodium + Sulphur + Water

Thiosulphate        +  Acid                                Chloride   Dioxide

Na2S2O3 (aq) + HCL (aq) ⇒ S(s) + 2NaCl (aq) + SO2 (g) + H2O (l)

There are many different things I can change which will affect the rate of reaction, so I will have to do preliminary experiments to find out ideal quantities for my final experiment.  Below are some variables I can change for my experiments:

  • Temperature
  • Concentration of Sodium Thiosulphate
  • Concentration of Hydrochloric Acid
  • Volume of Sodium Thiosulphate
  • Volume of Hydrochloric Acid
  • If I stir the experiment or let it stand

For this reaction I will have to decide a suitable quantity of Sodium Thiosulphate and Hydrochloric acid during my preliminary investigations, then I will have to decide whether I will be changing the concentration of the Hydrochloric Acid or the Sodium Thiosulphate.  The reaction takes place relatively quickly and relies on the naked eye.  I will be having to time how long it takes for an image below the conical flask in which the reaction taking place, gets entirely obscured by the build up of sulphur.

I predict that the more concentrated the Sodium Thiosulphate, the faster it will react.  This is because there are more molecules and more Sodium Thiosulphate, so they are more likely to collide making the reaction faster.  I also think that when the concentration is lower, the reaction will take place slower.

In the low concentration, 50% concentration on the Sodium Thiosulphate, you can see that although there are the same amount of molecules, there is water which the Hydrochloric acid will also ‘bump’ into.  This means that the Hydrochloric acid is less likely to ‘bump’ the Sodium Thiosulphate molecules and thus, make the reaction slower.

Join now!

Activation Energy is the amount of energy required for a reaction to take place.  As a reaction takes place two molecules approach each other and then repel, the energy required to force the two particles to collide is activation energy, the particles then get close enough to rearrange the electron shells.  Using a catalyst lowers the amount of activation energy required for the electrons to be rearranged.   As shown below.

I predict that the graph for my main experiment will look like this:

Method

For the preliminaries I will be testing how ...

This is a preview of the whole essay