Description of experiment
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Needed compounds:
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hydrogen peroxide : H2O2
ammonia : NH3
cobaltosic oxide : Co3O4
Class:
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elem=Co
coordination
redox
Summary:
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Cobalt forms many complexes with ammonia and it forms these complexes
easily, but when cobaltosic oxide (Co3O4, black oxide) is used, then no
such reactions can be observed. Co3O4 appears to be very inert.
Description:
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Add some Co3O4 to ammonia (appr. 25% by weight): No reaction, the solid does
not dissolve, the liquid remains colorless (once the solid has settled on
the bottom).
Add a little H2O2 (appr. 10% by weight): No visible reaction, besides some
slow decomposition of H2O2. The liquid remains colorless, no Co3O4 dissolves.
Heat liquid: Liquid starts foaming, a large amount of NH3 is expelled (smell!).
Probably the H2O2 also decomposes at a higher rate and it is expected that
the gas, escaping from the liquid is a mixture of NH3 and O2. When the liquid
cools down, then still some gas is evolved (probably due to decomposition of
H2O2), but no Co3O4 has dissolved. The liquid remains colorless.