Extraction of zinc from zinc blende is achieved by

electrolytic reduction
roasting followed by reduction with carbon
roasting followed by reduction with another metal
roasting followed by self-reduction

Solution

Extraction of Zn from ZnS(Zinc blende) is achieved by roasting followed by reduction with carbon.
2ZnS + 3O₂ ⟶ 2ZnO +2SO₂
ZnO + C ⟶ Zn + CO

Pb and Sn are extracted from their chief ore by

carbon reduction and self reduction.
self reduction and carbon reduction
electrolysis and self reduction.
self reduction and electrolysis.20.Extraction of zinc from zinc blende is achieved by

Solution

Which of the following factors is of no significance for roasting sulphide ores to the oxides and not subjecting the sulphide ores to carbon reduction directly?

Metal sulphides are thermodynamically more stable than CS₂
CO₂ is thermodynamically more stable than CS₂
Metal sulphides are less stable than the corresponding oxides
CO₂ is more volatile than CS₂

Solution

The reduction of metal sulphides by carbon reduction process is not spontaneous because ∆G for such a process is positive. The reduction of metal oxide by carbon reduction process is spontaneous as ∆G for such a process is negative. From this we find that on thermodynamic considerations CO₂ is more stable than CS₂ and the metal sulphides are more stable than corresponding oxides.In view of above the factor listed in choice (c) is incorrect and so is of no significance.

Duraluminium is an alloy of

Al and Mg
Al, Mg and Ni
Al, Mg, Mn and Cu
Al and Ni

Solution

Duraluminium alloy contains Al (95%), Cu (3%), Mn(1%), Mg (1%).

Aluminium is prepared in large quantities by

heating cryolite in a limited quantity of air
reducing aluminium oxide with coke
reducing aluminium oxide with sodium
electrolysing aluminium oxide dissolved in fused electrolyte

The compound that can work both as an oxidising agent and a reducing agent is

KMnO₄
H₂S
BaO₂
H₂O₂.

Solution

In froth floatation process, ore particles float because their surface is hydrophobic i.e.,not easily wetted by oil.

Which is not a basic flux ?

CaCO₃
Lime
SiO₂
CaO

Solution

SiO₂ is an acidic flux.

Bauxite ore is made up of Al₂O₃ + SiO₂ + TiO₂ + Fe₂O₃. This ore is treated with conc. NaOH solution at 500 K and 35 bar pressure for few hours and filtered hot. In the filtrate the species present, is/are

NaAl(OH)₄ only
Na2Ti(OH)₆ only
NaAl(OH)₄ and Na2SiO₃
Na₂SiO₃ only

Solution

Sulfide ores are common for the metals

Ag, Cu and Pb
Ag, Mg and Pb
Ag, Cu and Sn
Al, Cu and Pb

Solution

Silver, copper and lead are commonly found in earth's crust as Ag₂S (silver glance), CuFeS₂(copper pyrites)and PbS (galena).

Which statement is correct ?

Gangues are carefully chosen to combine with the slag present in the ore to produce easily fusible flux to carry away the impurities
Slags are carefully chosen to combine with the flux present in the ore to produce easily fusible gangue to carry away the impurities
Gangues are carefully chosen to combine with the flux present in the ore to produce easily fusible slag to carry away the impurities
Fluxes are carefully chosen to combine with the gangue present in the ore to produce easily fusible slag to carry away the impurities

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