Essay About Rates Of Reaction Sodium Thiosulphate And Fair Test

Chemistry
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rates of reaction Sodium Thiosulphate + Hydrochloric Acid
Na2S2O3 (aq) + 2HCl (aq)
Sodium Chloride + Water + Sulphur Dioxide + Sulphur
2NaCl (aq) + H2O (l) + SO2 (g) + S (s)
Fair Test
To make this experiment a fair test, we need to make sure we do a
number of things. In this experiment we are trying to find the rate of
reaction using concentration as a factor, so there is a number of
things we need to make sure we do to keep it a fair test.
Firstly, we need to keep a chemical at a constant concentration. So,
in this experiment we have chosen to keep hydrochloric acid at a
constant concentration (5cm3). We could have, however, used Sodium
Thiosulphate as a constant, but we had chosen to use Hydrochloric
acid.
Next we must make sure that the solution is kept at a constant volume
throughout the experiment. If the volume is different, then it could
give different results to if it was at a constant volume. We must also
make sure that we add both the water and the Sodium Thiosulphate at
exactly the same time (into the beaker with the hydrochloric acid in
it), or it could affect the results of the experiment.
We must start the stopwatch at the exact time as we put the water and
the Sodium Thiosulphate into the beaker. To do this it is a lot easier
if there are two people doing the experiment, so one person can put
the two substances in the HCL, and one person can start the stopwatch.
Also The person timing the experiment will look for the disappearance
of the cross, otherwise there would be a time lapse between seeing the
cross disappear and telling the other person to stop the clock and
then eventually stopping the clock.
It is also important