Factors Affecting - Concentration of Reactants

The higher the concentration of the solution, the higher the rate of reaction.

Experiment

By measuring the time taken for the formation of sulphur precipitate (yellow solid) when sulphuric acid, H2SO4 reacts with sodium thiosulphate(VI), Na2S2O3 of different concentration , we can investigate the effect of concentration of the reactant on the rate of reaction.

Procedure:
1. 50 cm3 of 0.2 mol dm-3 sodium thiosulphate solution + 10 cm3 of 0.5 mol dm-3 sulphuric acid.
2. Time taken for the ̔X’ sign placed under the conical flask to disappear from view is recorded.
3. The experiment is repeated by using sodium thiosulphate solution with concentration 0.4 mol dm-3, 0.6 mol dm-3, 0.8 mol dm-3 and 1.0 mol dm-3.
Conclusion 1:

1. The graph for concentration of sodium thiosulphate (VI), Na2S2O3 against time taken for the sulphur precipitate to formed is plotted.
2. As the concentration of sodium thiosulphate solution decreases, the longer the time is needed for the marked ̔X’ to disappear.
Conclusion 2:

1. The graph for concentration of sodium thiosulphate (VI), Na2S203 against 1/time taken is plotted.
2. As the concentration of sodium thiosulphate increases, the value of 1/time increases. We should note that 1/time = rate of reaction.
3. The higher the concentration of sodium thiosulphate solution, the higher the rate of reaction .