Q60 of 65 Page 26

Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores.

Extraction of metals of low reactivity: Mercury is a less reactive metal. The ore of mercury is called cinnabar, i.e. mercury (II) sulphide. The ore is heated in air and is oxidized to produce mercury (II) oxide. Mercury oxide is reduced to obtain mercury. The following reactions are involved in this process.


2HgS + 3O2→ 2HgO + 2SO2


Extraction of metals of medium reactivity: The metals in the middle of the reactivity series are also extracted by roasting followed by the process of reduction but the methods are somewhat different. Let’s take the example of zinc.


Extraction of Zinc: Zinc is placed in the middle of the reactivity series. It occurs as zinc blende (zinc oxide). It is first heated in the presence of air to obtain zinc oxide. This process is shown by following equation:


2ZnS + 3O2→ 2ZnO + 2SO2


After that, zinc oxide is reduced to obtain pure zinc metal. The reduction is done in the presence of carbon. This can be shown by following equation.


ZnO + C Zn + CO


More from this chapter

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58

A solution of CuSO4 was kept in an iron pot. After few days the iron pot was found to have a number of holes in it. Explain the reason in terms of reactivity. Write the equation of the reaction involved.

 59

A non-metal A which is the largest constituent of air, when heated with H2 in 1:3 ratio in the presence of catalyst (Fe) gives a gas B. On heating with O2 it gives an oxide C. If this oxide is passed into water in the presence of air it gives an acid D which acts as a strong oxidising agent.

(a) Identify A, B, C and D.


(b) To which group of periodic table does this non-metal belong?

 61

Explain the following.

(a) Reactivity of Al decreases if it is dipped in HNO3


(b) Carbon cannot reduce the oxides of Na or Mg.


(c) NaCl is not a conductor of electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state.


(d) Iron articles are galvanised.


(e) Metals like Na, K, Ca and Mg are never found in their free state in nature.

 62

(i) Given below are the steps for extraction of copper from its ore. Write the reaction involved.

(a) Roasting of copper (I) sulphide


(b) Reduction of copper (I) oxide with copper (I) sulphide.


(c) Electrolytic refining


(ii) Draw a neat and well labelled diagram for electrolytic refining of copper.