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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.

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Introduction

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. ...read more.

Middle

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: Volume of sodium thiosulphate solution (cm3) Volume of water (cm3) Time taken for the cross to disappear (s) Concentration of the sodium thiosulphate solution (g/dm3) Rate of the reaction (/s) 50 0 34 40 0.02941176 40 10 41 32 0.02439024 30 20 52 24 0.01923077 20 30 89 16 0.01123596 10 40 319 8 0.0031348 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. ...read more.

Conclusion

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: - It was much more accurate as explained above. - The work could be done for you once the experiment had started! - The graph showed the exact fall of light getting through. ...read more.

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