4. Into another 250cm^3 conical flask, 50cm^3 of 0.02 mol.dm^-3 iodine solution will be added.
5. Into another 250cm^3 conical flask, 25cm^3 of 1 mol.dm^-3 sulphuric acid and 25cm^3 of 1 mol.dm^-3 propanone solution will be added.
6. The iodine solution will be mixed with the acid and propanone into one conical flask and the stopwatch will be started.
7. The mixed solution will be stirred for one miute and every five minutes for 35 minutes 10cm^3 of the mixture will be pippetted the conical flasks containing the sodium hydrogen carbonate. NB: The mixture must be added into the right conical flask i.e. after five minutes the first withdrawal must be put into the flask that says five minutes etc.
8. Into each of the conical flasks containing the new mixture, a few drops of fresh starch solution will be added.
9. Another burette will be washed out and filled up with 0.01 mol.dm^-3 sodium thiosulphate solution.
10. Carefully, the sodium thiosulphate will be titrated against the (iodine/propanone/acid/carbonate) mixture in conical flask labelled 5 mins until the solution temporarily turns colourless.
11. The end point will be near so the sodium thiosulphate must be added drop by drop until the solution turns colourless for more than 30 seconds.
12. The titre will be read off the burette by seeing where the bottom of the meniscus lies on.
13. Steps 10-12 will be repeated for all the 6 remaining conical flask.
14. Steps 3-13 will be repeated in order to gain an average of all three titrations.
NB: The three average titrations for each time must be at least within 0.5ml to eachother in order for them to be valid.
15. The exact temperature of the solution will be recorded.
16. Steps 3-13 will be repeated for approximately 30, 40, 50 and 60 degrees centigrade by placing the solutions into a water bath before reacting them.
NB: The temperatures do not need to be exactly as stated in step 16 but the exact temperature must be recorded.
