The Effect of Concentration on the
Reaction between Sodium
Thiosulphate and Hydrochloric Acid.
We are given 2md/dm³ of Hydrochloric Acid = 10cm³. We are also given the measurement of Sodium Thiosulphate solution: 40g/dm³ = 50cm³
The chemical equation for this reaction is:
2Hcl + Na²S²O² 2NaCl + H²O + SO² + S
I am going to investigate the effect of concentration in this reaction. To do this I will change the volume of 0.1 mol/dm³ of sodium Thiosulphate. We will keep the amount of Hcl the same, because if we altar that one it will totally change the results and there would be no pattern. We learned that if the concentration doubles, the rate doubles. I will therefore choose the dilute sodium Thiosulphate to prove this and to see if it affects the rate of the reaction. Besides concentration I know that catalysts, temperature and surface area also affect the rate of the reaction. Therefore I think that the less concentration of sodium Thiosulphate the slower the rate of the reaction will go. We did preliminary work on this experiment, I took a conical flask and put 50cm³ of sodium Thiosulphate and added 10cm³ of Hcl. Under the conical flask I put a white piece of paper and put a black cross on it. We made sure that our cross was very dark and think because if it was just a thing cross you might not see it so well and think it has disappeared even though with a thicker cross you can still see it. This is how we set it up: