I am going to investigate how a change in concentration affects the reaction rate between Sodium Thiosulphate and Hydrochloric acid. The chemical equation for the experiment is as below;.
Na2S2O3 + 2HCl 2NaCl + H2O + S + SO2.
When pouring the acid, make sure it is done above eye level. Hydrochloric acid is also an irritant, so goggles could be used. .
Always wash your hands after doing an experiment, especially ones with irritant.
The reaction gives off Sulphur Dioxide, which is a highly acidic gas, so as soon as the reaction has finishes, it all needs to be washed down the sink with plenty of water. .
Two small 100cm3 beakers, for the Sodium Thiosulphate and Hydrochloric acid.
A small 100cm3 conical flask to mix the fluids in.
A small conical flask that has a capacity of 35cm3 .
A piece of lined paper, to judge when the reaction has finished.
A stop-clock to determine the duration of the reaction.
A calculator to work out the average reaction rate.
A total of 280cm3 Sodium Thiosulphate.
A total of 80cm3 Hydrochloric acid.
A total of 280cm3 water.
A pilot study was conducted to see if the reaction being investigated actually worked, and if the amounts and concentrations were effective. The results were as follows;.
Vol. Of Thiosulphate Vol. of acid (cm3 Vol. Of water (cm3) Time 1 (s) Time 2 (s) Time 3 (s) Average (s) Rate (s-1).
35 10 0 21 20 19 20 50.
30 10 5 21 23 20 21 48.
25 10 10 28 30 28 29 34.
20 10 15 39 37 33 36 25.
15 10 20 46 43 46 45 22.
10 10 25 76 72 68 72 14.
5 10 30 178 175 164 172 6.
0 10 35 NR NR NR NR NR.
From these results, I can determine whether the experiment was a success and whether I can learn from my mistakes. All decimals have been rounded up or down to the nearest whole number. .
To make the experiment fair, there was only one variable. This was the concentration of the Sodium Thiosulphate solution.