Iodine Clock Reaction Lab Report

Manipulation of the Iodine Clock Reactions
Haden G. Cavalli
HL 1 Chemistry IA

Introduction I am involved in a club at my local high school where we try new fun experiments in the classroom together in order to advance our understanding of science outside of the classroom. While I was looking for ideas, I found the iodine clock experiment which is where “A solution of hydrogen peroxide is mixed with one containing potassium iodide, starch and sodium thiosulfate” in order to create a mixture where the solution suddenly turns a dark blue color ("Iodine Clock," 2015). I had been thinking how I could turn this into a fun competition and how I could manipulate the experiment when I thought that I could try to experiment to find

persulfate variation. This is the third of the four main forms of the iodine clock reactions where iodide ions is reacted with persulfate in 2 main reactions. The total reaction is the reaction of sodium and iodide ions, as well as sodium thiosulfate, which is then reacted with the starch to form the bluish color. As seen in figure 6, the first reaction consists of peroxydisulfate (), and iodide ions which form iodine and sulfate (SO42-). The first reaction is to change the iodide ions to iodine so they can be later changed back to iodide ions to react with the starch, to form the blue colored reaction.
Variables
Dependent: I am testing the time it takes to react certain solutions, so the dependent variable is the time of the reaction in seconds.
Independent: I am manipulating the amount of solution that is being reacted, so they independent variable is the amount of solution in

The most important aspect of determining the results is the timing. The timing will be used with a stopwatch, and will be timed from the moment that all the solution have been combined, and will end at the point that the solution has completely finished changing colors. In order to add the solution, and start the timer at the same time, I will need a second person to time while I combine the solutions together. In order to maintain similar results, I will also need to keep the same person keeping track as they will start and end the timer at the same time when they see fit in all the reactions.
Procedure
Reaction 1
Solution A (in a 100 mL graduated cylinder)
10 mL of 2.0M of sulphuric acid
10 mL of 3% hydrogen peroxide
80 mL water
Solution B (in a 100mL graduated cylinder)
Solution of .04 grams of sodium thiosulfate pentahydrate in 20 mL of water
Solution of .9 grams of potassium iodide in 5 mL of water
4 mL starch solution
71 mL of water
Combine the solutions in a flask and stir (hand or magnetic stirrer) until turns dark blue
Immediately start timing at the moment that the solutions combine together

Observation Table (sample data)
Experiment 1:
Hydrogen Peroxide (mL)
Time (seconds)
1