ANALYSIS OF THE DECOMPOSITION OF

HYDROGEN PEROXIDE Chem 464 Brigham Young University Idaho

Jessica L. Ward; Erich Kumpunen; Johnny Mackey

1

Pressure

Tem

p

KMnO

2

H2SO4H2O2

KMnO2 H2O2Catalyst

2

Introduction

Every chemical reaction occurs at a particular rate, dependent on temperature. Current theories show that reactions evolve through pathways and intermediates, with a single, rate limiting step within that pathway. From this rate-limiting step, activation energy and reaction rates can be determined using chemical kinetics and the Arrhenius equations.

3

4

•The original apparatus design

•Too crude to use in the conditions required

•Pressure leaks were everywhere

•Plastic melted within a 20 K shift

5

•The final apparatus

•Worked much more effectively

•Still failed with pressures over about 1.2 atm

•...unless wrapped with electrical tape

• Hydrogen peroxide (H2O2) is a powerful oxidizer, and violently reacts with certain catalysts releasing large amounts of heat very quickly. If using in large amounts, stay in the fume hood. Always use goggles, gloves, and a lab coat. Dispose of excess by decomposing with potassium iodide, then flush down the sink with large amounts of water.

• Sulfuric acid (H2SO4) is a strong acid, and will cause severe burns to skin or eyes. If contact occurs, rinse affected area for at least 15 minutes with water, and apply baking soda to neutralize as needed.

• Potassium iodide (KI) is a common salt substitution for traditional table salt. Over-exposure can cause irritation, however, so goggles and gloves should be worn. Can be disposed of in the sink.

• Manganese dioxide (MnO2) is an irritant with a heavy metal, and should not be breathed in. Can stain skin, but is easily washed off. MnO2 should be disposed of in a heavy metal waste container.

• Potassium permanganate (KMnO4) is a strong oxidizer, and is an environmental hazard and so should not be flushed down the sink.. Avoid contact with skin. KMnO4 should be disposed of in a heavy metal waste container.

Hazard Analysis

6https://www.msdsonline.com/msds-search

• Decomposition of hydrogen peroxide with a catalyst is a 1st order reaction

• Rate of reaction is dependent on concentration of the catalyst

• Rate constant, rate, and activation energy can be calculated from the change of pressure, and temperature.

• Temperature affects the catalytic decomposition of hydrogen peroxide

7

Claims

2MnO4-(aq)+5H2O2(aq)+6H+(aq)→2Mn2+(aq)+5O2(aq)+8H2O(aq)

• Redox titration using KMnO4 was used to determine actual concentration

• KMnO4 is an extremely potent catalyst

• H2O2 concentration decayed from 38%-34%

Determination of H2O2 Concentration

8

• Table 1 rates and Kat different temperatures with different catalysts

9

Temperature (K)

Rate (atm/sec)

K (1/sec)

KI 298 4.42e-5 1.11e-3

MnO2 298 3.0e-5 2.3e-4

KI 315 2.98e-3 7.5e-3

MnO2 315 7.6e-6 6.4e-5

KI 325 8.6e-5 1.66e-3

MnO2 325 3.6e-5 6.9e-4

Evidence and Analysis

• http://www.chemguide.co.uk/physical/basicrates/arrhenius.html• http://www.livingston.org/cms/lib9/NJ01000562/Centricity/D• omain/826/AC%2028%20Hydrogen%20Peroxide%20Decomposition%20S.doc.

10

MnO2 KI

Activation Energy Calculated -11.4 kJ/mL 58.08 kJj/mol

Activation Energy Literature Value 58 kJ /mol 56.5 kJ/molhttp://www.science.uwaterloo.ca/~cchieh/cact/c123/ea_catalyst.html http://ocw.mit.edu/high-school/chemistry/demonstrations/videos/the-steaming-gun/steaming_gun.pdf http://pubs.acs.org/doi/pdf/10.1021/ed400002t

• The decomposition of H2O2 is a very slow process without a catalyst

• H2O2 will decompose if in contact with an oxidizing agent

• For more accurate results, many, many more trials are necessary

• Thermodynamic equations really work the way they’re supposed to!

Reflections

11

More Reflections•Even one atmosphere is a lot of pressure

•2000 seconds is 45 minutes

•A “simple” research project does not exist

•There are many different types of titrations

•KMnO4 is a stronger catalyst than any of those originally suggested

12

Acknowledgements • Brother Becerril • Tyler Southam • Brother Dabell • Jessica Simpson • Amanda Huntsman • BYUI Chemistry Department

13