Colourful Solutions > Practical Scheme of Work > E111: Formula by reduction of a metal oxide (virtual)

IB Chemistry Shop

Standard level

Chemical compounds contain elements in an exact mole ratio. This mole ratio gives the formula of the compound. Two elements may form between one and many compounds, each with a different specific ratio of moles.

For example, hydrogen and oxygen form two completely different compounds, water and hydrogen peroxide with formulae H2O and H2O2 respectively.

Many metals form several oxides, each with a different ratio of the elements.


Background

Oxides of relatively unreactive metals can be reduced to metal by heating in a flow of hydrogen or methane gas.

Reduction of copper(II) oxide

CuO(s) + H2(g) Cu(s) + H2O(g)

If the mass of the metal oxide is recorded and the mass of the metal residue is also recorded, the mass of oxygen lost can easily be determined.

The mol of oxygen can then be calculated and if the identity of the metal is known, the formula of the metal oxide can be determined.

This experiment can be performed in the laboratory, if suitable safety precautions are taken.


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Requirements


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Procedure


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Safety precautions

Although the reaction can be performed in the laboratory as a demonstration or student experiment, there are some safety issues to be aware of.


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Teaching resource

The animation can be projected full screen here.


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