Oxidation and Reduction of Copper
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A piece of copper is supported over a burner and is heated. The copper begins to react more rapidly with oxygen from the air and a darker color can be seen on the surface of the copper. This is similar to the color that forms on copper cookware when it is used in a kitchen. A few seconds later the copper has become dark. It has reacted with oxygen in the air. The burner flame is turned out, and an inverted funnel with hydrogen gas blowing out of it is placed over the copper. The hydrogen gas is a reducing agent. It reduces the copper oxide on the surface of the copper and causes pure copper to be formed again. The dark color disappears, leaving a pure copper color. Oxidation and reduction of the copper can be repeated several times by removing and replacing the funnel until the metal cools and the reactions slow down.
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© 1997 Division of Chemical Education, Inc., American Chemical Society. All rights reserved.