IB Chem HL Richard Forster
March 20, 2013
In this experiment, a reduction of peroxodisulphate (VI) ions by iodine ions is investigated. Solution of 10cm3 of K2S2O8, potassium peroxodisulphate, represented as ‘Solution A’. Mixture of 5cm3 of KI (Potassium iodide solution), and 5 cm3 of Na2S2O3 (sodium thiosulphate solution), and 2.5cm3 of starch solution is considered as ‘Solution B’. Solution A and B are mixed together under different temperatures to show a “clock” reaction.
Table 1: Raw Quantitative Data of Temperature and Time from the Experiment Fixed / Ideal Temperature (°C)| Temperature of Solution A (°C±0.5°C)| Temperature of Solution B (°C±0.5°C)| Time Taken| Time Proceeded (seconds±1 seconds)| 30| 31.0| 31.0| 3:10:34| 191|
35| 36.0| 33.5| 2:11:83| 132|
40| 40.0| 38.0| 1:37:24| 97|
45| 46.0| 45.5| 1:12:83| 73|
50| 51.0| 51.0| 0:52:40| 53|
Before: Solution A: clear colorless solutions; Solution B: clear colorless solution During: Both solution A and B reached (or close to) a fixed temperature and mixed together form a clear colorless solution reaction time: one or few section of the solution turned clear light purple opaque purple, then the section expand to the entire solution speedily within a second the purple opaque solution gradually turn to a darker purple color After: Dark purple-black colored opaque solution
Processing and Presenting Data:
Table 2: Uncertainty of the Apparatus Used in the Experiment Equipment| Uncertainty| Explanation|
Stopwatch| Seconds±1 second| The actual uncertainty of the stopwatch is millisecond, shown in the column ‘Time Taken’ in Table 1. However, there are human reaction uncertainties when receiving the change in color in the actual experiment, so that particular uncertainty is presented by ±1 second| 50cm3 Burette for K2S2O8, KI, and Na2S2O3| cm3±0.02cm30.02%...