Our assignment was to produce a piece of coursework investigating the rates of reaction, and the effect different changes have on them.

Aim: -

To see the effects of a change in concentration on the rate of a reaction.

Sodium Thiosulphate + Hydrochloric Acid = Sodium +water + sulphur dioxide

Na( S( 0( + 2HCl = 2Nacl +H(O + So(

We will be varying the concentration (while keeping everything else constant).

Both the sodium Thiosulphate and the Hydrochloric acid are soluble in water, so the concentration of either can be changed.

However I have chosen to vary the sodium Thiosulphate as it is available in larger amounts, and various concentrations are prepared.

I will decide the suitable range of concentration and many other things during my Trial run.

Prediction

I predict that as the concentration of the sodium Thiosulphate increases the rate of reaction will increase.

This means that both graphs drawn up in my analysis will have positive correlation, and will probably be curved as the increase in rate of reaction will not be exactly the same as the concentration is increased.

The reason I predict this is because if the concentration of a solution is increased there are more reactant particles. This increases the probability of reactant particles colliding with each other.

Apparatus

* Beaker

*Glass rod

*Conical Flask

*100cm( Cylinder

*10cm( Cylinder

*Stop Watch

*Balance

* X marked paper

Method: -.

First we measured the amount of crystals that we wanted

Then we added the crystals to the beaker.

After that we added the 100cm( of water to the beaker.

We then stir the crystals until they have completely dissolved.

This creates our Sodium Thiosulphate to the concentration that we needed.

We then placed the beaker over the X marked paper.

Then we add the Hydrochloric acid.

The stopwatch begins when all the acid has been added.

Finally we repeat the experiment for fair testing.

Fair Testing

To make sure it is a fair test we will be doing certain things such as:

* The same person on stop watch through out the experiment

* The same person judging if the cross has disappeared

* Make sure it's the same temperature [room temperature]

* Accurate measuring [using a pipette]

* Use a different pipette for the acid and the sodium.

Trial Run

The trial run of this experiment allowed me to figure out the correct measurement to use, to see what could be improved and also who should do what it the experiment.

We decided that the concentrations were going to range from 10g/unit - 60g/unit the reason for this is because anything lower than 10g/unit would take to long and anything higher than 60g/unit would be to fast and could be affected majourly by the reaction time of the person on the stopwatch.

End Results

To work out the rate of reaction you divide 1 by the time taken for the reaction to take place.

Analysis

In this experiment I have found out that the lower the concentration the lower the rate of reaction is.

I know this because my graph has a positive correlation and is almost a straight line, with a few out layers which could be due to human error during the experiment.

However using a line of best fit we can figure out what the rate of reaction should be.