Chapter 03 Metals And Non-metals Questions-04
Questions
1. Define the following terms.
(i) Mineral
(ii) Ore
(iii) Gangue
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Answer
(i) Mineral: Most of the elements occur in nature as in combined state as minerals. The chemical composition of minerals is fixed.
(ii) Ore: Minerals from which metals can be extracted profitably are known as ores.
(iii) Gangue: The impurities (sand, silt, soil, gravel, etc.) present in the ore are called gangue.
2. Name two metals which are found in nature in the free state.
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Answer
The metals at the bottom of the reactivity series are mostly found in free state. For example: gold, silver, and platinum.
3. What chemical process is used for obtaining a metal from its oxide?
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Answer
The chemical process used for obtaining a metal from its oxide is reduction. In this process, metal oxides are reduced by using suitable reducing agents such as carbon or by highly reactive metals to displace the metals from their oxides.
For example, zinc oxide is reduced to metallic zinc by heating with carbon.
$ ZnO _{(s)}+C _{(s)} \xrightarrow{\Delta} Zn _{(s)}+CO _{(g)} $
Manganese dioxide is reduced to manganese by treating it with aluminium powder. In this case, aluminium displaces manganese from its oxide.
$ 3 MnO _{2(s)}+4 Al _{(s)} \longrightarrow 3 Mn _{(f)}+2 Al_2 O _{3(s)}+\text{ Heat } $
Oxides of more reactive metals are reduced by electrolysis.
