Decomposition Reactions
Ammonium Dichromate Volcano
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The ammonium dichromate volcano illustrates what happens in a chemical reaction. The orange solid is ammonium dichromate. When a wick soaked in alcohol is placed into the ammonium dichromate and ignited with a match, the higher temperature causes the ammonium dichromate to start reacting. The darker material which is forming is evidence of a chemical change. As the reaction proceeds, it generates heat and the dark solid material is formed more rapidly. Flames and sparks can be seen shooting upward. The orange solid has been transformed into a dark gray-green solid and the temperature has changed. These observations are characteristic of a chemical reaction: a substance with one set of properties is transformed into one or more new substances, with a temperature change.
(44)
Equation
(NH4)2Cr2O7 ---> N2 + 4H2O + Cr2O3
© 1997 Division of Chemical Education, Inc., American Chemical Society. All rights reserved.