MadSci Network: Biochemistry

Re: Why do H2O2 and catalase/MnO2 release heat when mixed?

Date: Wed Sep 26 22:28:17 2007
Posted By: Tarun Gupta, Graduate Student - M.Sc. Human Genomics
Area of science: Biochemistry
ID: 1190841713.Bc

Hey Sean,

I would quote a line from a chemistry experiment book I found in that nasty smelling chemistry laboratory

"A large amount of MnO2 was liberated from Duracells, washed, and dried. A 1/4" diameter chunk was dropped into a dixie cup of H2O2. Reaction was vigorous, and immediate, sending steam all over the room."

The general Reaction is:

H2O2 -------> H2O + O2 
Manganese dioxide is an inorganic catalyst (but not an enzyme) for the breaking down of hydrogen peroxide. Catalase is a protein catalyst (enzyme) for the breaking down of hydrogen peroxide.

Hydrogen peroxide decomposes according to the summary reaction equation:

H2O2 (l) > H2O (g) + O2 (g) + Heat

The amount of heat released (at normal conditions) in this exothermic reaction is 98.31 kJ/mole

You see that there is a bond breakage and no bond formation. So, there is an overall decrease in energy and energy is liberated as heat.


1. Walter C. Schumb, Charles N. Satterfield and Ralph L. Wentworth, Hydrogen Peroxide, Reinhold Publishing Corporation, 1955.

Kind Regards,
Tarun Gupta

MSc Human Genomics
National Center for Human Genome Studies and Research
Panjab University

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