Page 25 - Curriculum Visions Dynamic Book

Reduction/oxidation with copper
In the laboratory copper oxide (a black compound) can be reduced to copper (a reddish brown element) by passing carbon monoxide over the heated powder.
In this demonstration the gas carbon monoxide is passed through a special glass tube with a hole in the side. An excess of carbon monoxide is passed over the heated copper oxide and the unused carbon monoxide is burned off where it emerges from the hole.
The carbon monoxide reacts with the hot copper oxide and produces carbon dioxide gas. Carbon dioxide will not burn, so there is no flame at the outlet.
When all of the copper oxide has been converted to copper, carbon monoxide is flowing through the tube once more, and it ignites in the presence of the Bunsen flame.
The Bunsen flame is turned off, but carbon monoxide is still swept through the tube until the copper cools. If oxygen were to get in the tube while the copper was still hot, then the copper and the oxygen would react and reform the oxide. This would be a redox reaction.
exothermic reaction: a reaction that gives heat to the surroundings. Many oxidation reactions, for example, give out heat.
redox reaction: a reaction that involves reduction and oxidation.
Also...
Carbon monoxide is a very good reducing agent that will convert metal oxides to pure metal in a high temperature environment. Notice that it can be produced within a coke fire by drawing in a blast of air. This is the principle behind the iron- making blast furnace and the steel furnace, as you will see on later pages.
 Hot black copper oxide is being reduced by passing carbon monoxide over it.
The oxygen from the copper reacts with the carbon monoxide gas to produce a noncombustible gas, carbon dioxide. As a result there is no flame at the outlet hole.
Oxidation of carbon monoxide and reduction of copper oxide
Copper oxide+ carbon monoxide ➪ copper + carbon dioxide
CuO(s) +
Carbon monoxide gas passed into tube
CO(g) ➪
Cu(s) +
CO (g) 2
 The copper oxide is reduced to red copper. There is no more oxygen and so the carbon monoxide burns with blue flame.
Gas outlet hole
Black copper oxide
Tube heated with a Bunsen burner flame
Notice that in this reaction the copper oxide has been reduced to copper and, at the same time, the carbon monoxide gas has been oxidised to carbon dioxide gas.
 Hot copper will slowly turn black as it reacts with oxygen in the air.
25
25