Clock reactions are chemical reactions which happen a certain amount of time after two chemicals have been mixed. The way in which my experiment works is… In my experiment I am investigating the effect on varying the amount of each of the two chemicals, Iodate and Sulphur Dioxide, compared to the time elapsed between adding the two chemicals together and the reaction taking place. To keep the experiment as a fair test, the total volume of both reactants must be the same each time. To get around this we will add varying amounts of water to the mixtures to keep the volume constant.
To give us enough scope for varying the amounts of reactants, we will use 40ml of reactants. This means we will start off with 20ml of each, and then continue to use 20ml of one, 15ml of the other and 5ml of water. Another factor required to keep the test fair is to keep a constant temperature, as this will probably have an effect on the time taken for the clock reaction. Here is how Pirates, constant.I will execute my experiment: 1) Put the required amount of water in a beaker 2) Put 20ml of one reactant in the beaker 3) Put the desired amount of the other reactant in the beaker and start the stopwatch.
4) Briefly stir the solution 5) Stop the stopwatch when the clock reaction takes place. I predict that both reactants will behave in the same way when their volume is decreased in the solution. i. e the time taken for the reaction will be the same if there is 15ml of SO2, 20ml of Iodate and 5 ml of water as if there was 20ml of SO2, 15ml of Iodate and 5ml of water. This is because; from my preliminary experiments I found out that neither solution is more important than the other, and equal proportions of SO2 and Iodate takes the shortest time to react.
From this, I also predict that the smaller the ratio of SO2 to Iodate, or Iodate to SO2, the longer the clock reaction will take to happen. The controlled variables are the amounts of SO2 and Iodate, and the resultant variable is the time between the mixing of the two reactants and the start of the reaction. The fixed variables are the volume of water, the temperature. We will also repeat the experiment three times and average the results to make sure any anomalous results don’t warp the shape of the best fit line on the graph. Observation.
Here is the table of results from my experiment: SO2 Iodate Water Time Time 2 Time 3 Average S. D Concentration Rate Iodate Water Time Time 2 Time 3 Average S. D Concentration Rate Analysis Because there are two variables which I controlled, I have plotted three graphs, one for when I used 20ml of Sulphur dioxide and decreased the amount of Iodate, one for when I used 20ml of Iodate and one rate over concentration graph which allows me to compare the two sets of results. This final graph uses the averages of the two sets of data.