Glycerol and potassium permanganate

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An almost complete reaction of glycerol and potassium permanganate

The chemical redox reaction between potassium permanganate and glycerol[1][2][3][4][5][6] is often used to demonstrate the powerful oxidizing property of potassium permanganate, especially in the presence of organic compounds such as glycerol. The exothermic (heat producing) reaction between potassium permanganate (KMnO4), a strong oxidizing agent, and glycerol (C3H5(OH)3), a readily oxidised organic substance, is an example of an experiment sometimes referred to as a "chemical volcano".[7][8]

Explanation[edit]

Potassium permanganate (KMnO4) is a dark violet colored powder. Its reaction with glycerol (commonly known as glycerin or glycerine) (C3H5(OH)3) is highly exothermic, resulting rapidly in a flame, along with the formation of carbon dioxide and water vapour:

14 KMnO4(s) + 4 C3H5(OH)3(l) → 7 K2CO3(s) + 7 Mn2O3(s) + 5 CO2(g) + 16 H2O(g).[1][3][4][5][6]

Crystalline potassium permanganate (KMnO4) is placed in an evaporating dish. A depression is made at the center of the permanganate powder and glycerol liquid is added to it. The white smoke-like vapor produced by the reaction is a mixture of carbon dioxide gas and water vapor. Since the reaction is highly exothermic, initial sparking occurs, followed by a lilac- or pink-colored flame.[9] When energy or heat is added to electrons, their energy level increases to an excited state. This state is short-lived, and once the electrons release the energy, they return to their normal energy levels.[2] During this process the energy is visibly observed as light.[10] When the reaction is complete, it leaves behind a grayish solid with green regions.[1][3][4][5][6]

Gallery[edit]

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References[edit]

Wikimedia Commons has media related to Chemical volcano.
  1. ^ a b c "Glycerol and KMnO4". University of Washington Department of Chemistry. Retrieved May 26, 2019.
  2. ^ a b Ernest, Z. (April 16, 2014). "Why do different elements make different color flames when you burn them?". Socratic. Retrieved May 26, 2019.
  3. ^ a b c "Oxidation of glycerol by potassium permanganate". Chemedxchange. Retrieved May 26, 2019.
  4. ^ a b c Summerlin, L. R. (1988). Chemical Demonstrations : A sourcebook for Teachers. Volume 1. 2nd ed. Washington, DC: American Chemical Society. p. 122. ISBN 978-0841215351.
  5. ^ a b c Shakhashiri, B. Z. (1983). Chemical Demonstrations, Volume 1: A Handbook for Teachers of Chemistry. University of Wisconsin Press: Madison, Wisconsin: University of Wisconsin Press. pp. 83–84. ISBN 9780299088903.
  6. ^ a b c Lister, T.; O'Driscoll, C.; Reed, N. (1995). Classic chemistry demonstrations. London, UK: Royal Society of Chemistry. pp. 65–70. ISBN 978-1-87034-338-1.
  7. ^ Lee, M. "Chemical Volcano". California State University, Northridge. Retrieved July 11, 2019.
  8. ^ "Chemical Volcano" (PDF). Homi Bhabha Centre for Science Education. Retrieved July 11, 2019.
  9. ^ "Spontaneous exothermic reaction". The Royal Society of Chemistry. September 2016. Retrieved May 2, 2020.
  10. ^ Clark, Jim. "Flame Tests". chemguide. Retrieved July 11, 2019.
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