Investigation to find the effects of different concentrations of sodium thiosulphate mixed with hydrochloric acid. We wanted to find a precise set of results so we used a laptop computer to record the experiment.

AIM 2:

For this experiment we had the same aim as the first experiment (i.e. to find the effects of different concentrations of sodium thiosulphate mixed with hydrochloric acid). Although this time we wanted to find a more precise set of results so we used a laptop computer to record the experiment.

APPARATUS:

The apparatus used included: a flask, a measuring cylinder, an empty flask lined with black paper, a laptop computer and a sensor lamp.

METHOD 2:

We put sodium thiosulphate into the flask and some dilute sulphuric acid into the cylinder; water was also prepared so that it could be used to mix with the sodium thiosulphate. In addition to this the laptop computer was connected to the sensor lamp, which pointed into the empty flask lined with black paper. For the first experiment we added the two liquids and then began the program on the laptop. This program is used to record the time taken for the mixture to turn opaque in 2 minutes. When the lamp’s light is cut off from the sensor, it means the reaction has finished. For the second experiment, instead of pure sodium thiosulphate being added to the hydrochloric acid, some of it was replaced by water. In this way the experiment shows how long it takes for the reaction to take place using different concentrations of sodium thiosulphate. Five experiments were intended to be performed in total (although we only managed to do 2 of them in the time allotted), for each one a smaller concentration of sodium thiosulphate was used.

CHANGES OF PLAN:

The only change of plan which was made, was that the volume of sodium thiosulphate was decreased from the original agreed amount.

RESULTS:

GRAPH OF RESULTS:

GRAPHS OF EXPERIMENT:

50cm3 of sodium thiosulphate at a concentration of 40g/dm3

30cm3 of sodium thiosulphate at a concentration of 24g/dm3

In the first graph it is clear to see that after one minute’s time, only about 3.075 of the channel of light is remaining.

But in the second graph it is clear that after one minute’s time, ...

This is a preview of the whole essay

CHANGES OF PLAN:

The only change of plan which was made, was that the volume of sodium thiosulphate was decreased from the original agreed amount.

RESULTS:

GRAPH OF RESULTS:

GRAPHS OF EXPERIMENT:

50cm3 of sodium thiosulphate at a concentration of 40g/dm3

30cm3 of sodium thiosulphate at a concentration of 24g/dm3

In the first graph it is clear to see that after one minute’s time, only about 3.075 of the channel of light is remaining.

But in the second graph it is clear that after one minute’s time, the channel of light is still over 3.1. The reason for this is because there is water mixed in with the sodium thiosulphate, so it takes longer for the acid particles and the sodium thiosulphate particles to collide and cause a reaction. Therefore, less sulphur is produced as quickly so it takes longer for the mixture to turn opaque.

CONCLUSION:

My prediction was correct, I said that as the concentration of sodium thiosulphate increases so does the rate of reaction, and I was correct; this is proved in the graph. The reason why the rate of reaction increases with the concentration is because the more acid particles there are, the more reactions take place so the faster the experiment takes place. This is shown in the second experiment because there are less sodium thiosulphate particles the experiment therefore takes longer for them to collide with sulphuric acid particles causing a slower full reaction.

EVALUATION:

I was surprised to find out that in the beginning of the 2nd graph of method 2, the channel of light increased dramatically. I discovered that the reason for this was because somebody’s hand accidentally covered up the beam of light for a second when the chemicals were being poured into the flask.

There is unfortunately not enough evidence to support my conclusion because we only managed to perform two of the possible five experiments.

I believe that data-logging software was an improvement because it was far more accurate as the computer could make recordings once every 0.5 seconds!

The advantages of the data-logging method were these: