The most important ore of tin is :

cassiterite
cryolite
cerussite
none of these

Solution

Cassiterite ⟶ SnO₂

1–B, 2–A, 3–C, 4–D
1–B, 2–C, 3–A, 4–B
1–C, 2–A, 3–B, 4–D
1–C, 2–D, 3–A, 4–B

Solution

Ti – van-Arkel method
Si – Zone refining method
Al – Bauxite (Al₂O₃)
Pb –Cerussite (PbCO₃)

In Hall’s process, the main reagent is mixed with:

NaF
Na₃AlF₆
AlF₃
none of these

Solution

Na₃AlF₆ ⟶ Cryolite
Al₂O₃ is mixed with cryolite.Cryolite improves the electrical conductivity of the cell as Al₂O₃ is a poor conductor. In addition, the cryolite serves as an added impurity and lowers the melting point of the mixture to about 950°C.

Hydro-metallurgical process of extraction of metals is based on

complex formation
hydrolysis
dehydration
dehydrogenation

Solution

For example, Ag₂S is converted into Na[Ag(CN)₂].When Zn is added, Ag is displaced.

In order to refine “blister copper” it is melted in a furnace and is stirred with green logs of wood. The purpose is

to expel the dissolved gases in blister copper.
to bring the impurities to surface and oxidize them.
to increase the carbon content of copper.
to reduce the metallic oxide impurities with hydro carbon gases liberated from the wood.

Solution

The sulphide ore of copper is concentrated by

chemical method
froth floatation method
magnetic method
none of these

Solution

Froth floatation process is used for the concentration of lighter ores (sulphides) like CuFeS₂(copper pyrite).

If the impurities in a metal has a greater affinity for oxygen and is more easily oxidised than the metal, then the purification of metal may be carried out by

distillation
zone refining
electrolytic refining
cupellation

In the extraction of Cu, the metal is formed in the bessemer converter due to the reaction :

Cu₂S + 2Cu₂O ⟶ 6Cu + SO₂
Cu₂S ⟶ 2Cu + S
Fe + Cu₂O ⟶ 2Cu + FeO
2Cu₂O ⟶ 4Cu + O₂

Solution

Decomposition of carbonates and hydrated oxides.

A metal which is refined by poling is

sodium
blister copper
zinc
silver

Solution

Poling is used for purification of metal which contain their own oxide as impurity e.g., Cu₂O in Cu, SnO₂ in Sn etc.

Van Arkel method of purification of metals involves converting the metal to a

volatile stable compound
volatile unstable compound
nonvolatile stable compound
None of the above

Solution

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