Determining Activation Energy

Activation energy of a reaction Mengyuan Wu IB Chem HL Richard Forster March 20, 2013 Introduction: 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.

Observation: 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.

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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| Qualitative: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% for each solution| Initial Reading (±0. 1cm3) + Final reading (±0. 1cm3) = volume used (±0. cm3) for every solution measured in mixture A or B| 10mL Measuring Cylinder for starch solution| mL±0. 2mL| | Thermometer| °C±1. 0°C| Mixture A and B both have separate (but relatively close) temperature with uncertainty of ±0. 5°C each, after the average of the two the uncertainty doubles| Table 3: Processed date for temperature and time Average Temperature of the reaction (°C±1.

0°C)| Proceed Temperature (K±1. 0K)| Time Proceeded (seconds±1 seconds)| 31. 0| 304. 0| 191| 35. 0| 308.

0| 132| 39. 0| 312. 0| 97| 46. 0| 319. 0| 73| 51. 0| 324.

0| 53|Table 4: Processed data for Graphing ln 1t (3 sig fig)| 1T (K)(4 sig fig)| -5. 25| 0. 003289| -4. 88| 0.

003246| -4. 57| 0. 003205| -4. 29| 0. 003134| -3. 97| 0.

003086| ln 1t=lnK (Proportional) t= Time T= Temperature (in K) Graph1: Calculation: Values: Table 4: Calculation to Process Temperature: | | Calculation 1: Average Temperature (°C±1. 0°C)| Calculation 2: Temperature in K (K±1. 0K)| | Formula| Temp. of A+Temp.

of B2| Temp. in °C+273| Fixed / Ideal Temperature (°C)| 30| 31. 0+31. 02=31. 0| 31. 0+273=304. 0| | 35| 36.

0+33. 52=34. 75? 35. 0| 35. +273=308. 0| | 40| 40. 0+38.

02=39. 0| 39. 0+273=312. 0| | 45| 46. 0+45. 52=45. 75? 46. 0| 46.

0+273=319. 0| | 50| 51. 0+51. 02=51. 0| 51. 0+273=324. 0| Table 5: Calculation for Graphing Data | Calculation 3:ln 1t| Calculation 4:1T(K)| Fixed / Ideal Temperature (°C)| 30| ln1191? -5.

25| 1304? 0. 003289| | 35| ln1132? -4. 88| 1308? 0. 003246| | 40| ln197? -4. 57| 1312? 0. 003205| | 45| ln173? -4. 29| 1319? 0.

003134| | 50| ln153? -3. 97| 1324? 0. 003086| Calculation 5 (Activation Energy): lnk= -EaR ? 1T+lnA y = m(slope) x + c R=8. 314 Jmol-1K-1(Diploma)Data from Graph 1: y = -6045. 3x + 14. 705 -6045. 3 = -EaR Ea=8.

314 ? 6045. 3 =50260. 6242 J =50.

2606242 KJ Random Errors: Calculation 6: (%Random Error for Average Temperature of the Reaction) Average temperature of the reaction K ± 1. 0 K (Refer to Table 2) % Error=1. 0304. 0+1.

0308. 0+1. 0312. 0+1. 0319.

0+1. 0324. 0? 100 ? 1. 596% Calculation 7: (%Random Error for Time) Time Taken Seconds ± 1 Second (estimated human reaction time) (Refer to Table 2) % Error=1191+1132+197+173+153? 100? 5. 569% Calculation 8: (% Random Error for Solutions) Random Error for K2S2O8+KI+ Na2S2O3+Starch 0. 02%? 3+0.

22. 5? 100 ? 8. 06% Calculation 8: (Total % Random Error) % Error=1. 596%+5. 569%+8. 06% =15. 225%=20% (one sig. fig.

) Final Answer: Calculation 9: (Final Answer) 50. 2606242 KJ ±20% 50. 2606242 KJ =50. 3 KJ (3 sig. fig. >smallest sig.

fig. in calculation) 50. 2606242 KJ? 0. 2? 10. 052 KJ=10KJ (one sig. fig.

) Experimental Result: 50. 3 KJ ±10KJ 50. 3 KJ ±20% Work Cited: Diploma Programme Chemistry Data Booklet. 2nd ed. Cardiff: International Baccalaureate Organization, 2008.

6. Print.