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General Principles And Processes of Isolation Of Elements

Short Answer Type

51.

Give reason for the following: Although aluminium is above hydrogen in the electro-chemical series, it is stable in air and water.

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52.

An ore example of galena (PbS) is contaminated with zinc blende (ZnS). Name one chemical which can be used to concentrate galena selectively by froth floatation method.

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53.

Out of C and CO, which is better reducing agent at 673 K?

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54.

Why copper matte is put in silica lined converter?

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55.

Suggest a condition under which magnesium could reduce alumina.

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56. Although thermodynamically feasible, in practice, magnesium metal is not used for the reduction of alumina in the metallurgy of aluminium, why?

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57.

Why reduction of a metal oxide becomes easier if the metal formed is in liquid state at the temperature of reduction?

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58.

If at any site, low grade copper ores are available and zinc and iron scraps are also available. Which of the two scraps would be more suitable for reducing the leached copper ore and why?

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59.
Copper can be extracted by hydrometallurgy but not zinc. Explain.

Hydro metallurgy method is based on the fact that more electropositive metals displace less electro positive metals from their salt solution. Copper is precipitated from copper sulphate solution by adding iron.

CuSO₄ + Fe → FeSO₄ + Cu↓

But Zinc is not precipitated from zinc sulphate solution by adding iron. Hence copper can be extracted by hydro metallurgy but not zinc.

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