2206-008 Chemistry HL
Hypothesis The collision theory states effective collisions between reactant molecules must occur in order for the reaction to occur. The more reactant particles present, the more frequently they collide effectively, and the more often the reaction occurs to form products. Therefore, the increase in reactant concentration will increase the rate of reaction. Rate of reaction frequency of effective collision concentration of reactants
In this experiment, the concentration of one of the reactant, which is potassium iodide, is increased; this means that there will be more potassium iodide available to effectively collide with hydrogen peroxide as the concentration increases. As such, the hypothesis for this experiment is that the rate of reaction will increase with the concentration of potassium iodide.
Rate of reaction
The expected graph from this experiment is as follows:
Concentration of potassium iodide Figure 1: Expected graph of rate of reaction against concentration of potassium iodide
Variables Dependent variable
: Rate of reaction –
Independent variable
This can be determined by measuring the time taken for a mark “X” to be completely obscured by the blue-black of triiodide – starch complex. The inverse of the time taken is the rate of reaction.
: Concentration of potassium iodide –
0.1 mol dm-3 potassium iodide solution is prepared. The solution is then diluted to form potassium iodide solutions of different concentrations using dilution technique. 2