The Effect of Concentration on Reaction Rate

The Effect of Concentration on Reaction Rate

Introduction

I will be carrying out an investigation into how concentration affects

reaction rate. I will be looking at sodium thiosulphate and

hydrochloric acid. The reaction is represented by the following

equation:

[IMAGE]Na2S2O3(aq) + 2HCl(aq) 2NaCl(aq) + H2O(l) + SO2 (g) + S (s)

I will add the hydrochloric acid to the Sodium Thiosulphate and time

how log it takes for the mixture to turn opaque. I will use a

different concentration of Sodium Thiosulphate each time.

Prediction

My predictions, using previous knowledge is that the higher the

concentration of Sodium Thiosulphate there is the faster the reaction

rate will be.

This is based on the collision theory which I have outlined in

Background Knowledge.

In my preliminary work this has always been the case, for example if I

used 40 ml of Sodium Thiosulphate and 10 ml of water it was much

faster than when I used 10 ml of Sodium Thiosulphate and 40 ml of

water.

Background Knowledge

The rate of a reaction depends on two factors.

1) The number of collision per unit time between the reacting species.

2) The fraction of these collisions that are successful in producing a

mew molecule.

If two or more molecules collide but are not orientated correctly then

no reaction will take place. For a reaction to occur, molecules must

collide not only with sufficient energy but with the proper

orientation.

[IMAGE]

This diagram is the reaction between ethane, CH2CH2, and hydrogen

chloride, HCl.

In dilute Sodium Thiosulphate there are not so many particles. This

means that the chance of the particles colliding, and colliding

correctly is much less than if the Sodium Thiosulphate was

concentrated.

Apparatus

· Conical flask

· Burettes

· Measuring cylinder

· Funnels

· Thermometer

· Beakers

· Filter paper

· Sodium Thiosulphate

· Hydrochloric acid