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When hydrogen gas is passed through heated black copper (II) oxide, it:
reduces to form bluish copper solution
oxidises to form bluish copper solution
oxidises to form brownish copper metal
reduces to form brownish copper metal
reduces to form brownish copper metal
When hydrogen gas is passed over heated copper (II) oxide, a redox reaction occurs where copper (II) oxide is reduced to metallic copper. The black copper oxide loses oxygen and transforms into a brownish-red metallic copper residue.
When hydrogen gas is passed over heated copper (II) oxide, a redox reaction occurs where copper (II) oxide is reduced to metallic copper. The black copper oxide loses oxygen and transforms into a brownish-red metallic copper residue.
Think of it like a trade: Copper oxide is 'holding' oxygen tightly, and Hydrogen comes along, offering to take the oxygen away, leaving Copper 'free' and in its natural metallic state.
OIL RIG: Oxidation Is Loss (of electrons/hydrogen/gain of oxygen), Reduction Is Gain (of electrons/hydrogen/loss of oxygen).
CuO+H2тАЛ╬ФтАЛCu+H2тАЛO тАФ The chemical equation for the reduction of copper oxide by hydrogen
This is a classical redox (reduction-oxidation) reaction. Hydrogen acts as a reducing agent, removing oxygen from the copper (II) oxide. Simultaneously, hydrogen is oxidized to water vapor. The overall process is represented by the equation: CuO+H2тАЛтЖТCu+H2тАЛO.
Copper (II) oxide is black in color.
Metallic copper is brownish-red in color.
Hydrogen functions as the reducing agent in this reaction.
This reaction demonstrates the chemical displacement of oxygen from a metal oxide.
Useful method for extracting pure metals from metal oxides
Requires high temperatures
Hydrogen gas is highly flammable and poses safety risks
Laboratory preparation of pure metallic copper
Understanding industrial metallurgical reduction processes
Option A and B are incorrect as copper metal is distinctively brownish-red, not blue.
Option C is incorrect because the process involves reduction of the oxide, not oxidation of the copper.
D is correct тАФ The reaction involves the reduction of copper (II) oxide into brownish copper metal by the action of hydrogen gas.
Always remember that in a redox reaction, the substance that loses oxygen is 'reduced', and the substance that gains oxygen is 'oxidised'; this is a high-frequency question in competitive chemistry.
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