Aluminium is extracted from alumina (Al₂O₃) by electrolysis of a molten mixture of

1. Al₂O₃ + HF + NaAlF₄

2. Al₂O₃ + CaF₂ + NaAlF₄

3. Al₂O₃ + Na₃AlF₆ + CaF₂

4. Al₂O₃ + KF +Na₃AlF₆

Which one of the following is a mineral of iron?
(a) Malachite
(b) Cassiterite
(c) Pyrolusite
(d) Magnetite

In the extraction of copper from its sulphide ore, the metal is finally obtained by the reduction of cuprous oxide with

(1) copper (I) sulphide (Cu₂S)

(2) sulphur dioxide (SO₂)

(3) iron sulphide (FeS)

(4) carbon monoxide (CO)

Consider the following reactions at $1000°C.$

$\left(I\right) Zn\left(s\right)+1/2O_2\left(g\right)\stackrel{∆}{\to }ZnO\left(g\right);$
$∆G°=-360 kJ mo{l}^{-1}$
$\left(II\right) C\left(s\right) +1/2O_2\left(g\right)\stackrel{∆}{\to }Co\left(g\right);$
$∆G°=-460 kJ mo{l}^{-1}$

and choose the correct statement at $1000°C.$

(a) ZnO is more stable than CO

(b) ZnO can be reduced to Zn by C

(c) ZnO and CO are formed at equal rate

(d) ZnO can not be reduced to Zn by C

Chromium is obtained by reducing concentrated chromite ore with :

(a) red hot coke

(b) gaseous hydrogen 

(c) aluminium powder

(d) carbon monoxide  

The substance that acts as a collector in the froth flotation method is:

1. Sodium xenate.           

2. Sodium pyrophosphate.

3. Sodium nitroprusside.

4. Sodium ethyl xanthate. 

In the purification of impure nickel by Mond's process, metal is purified by:

(1) Electrolytic reduction

(2) Vapour phase thermal decomposition

(3) Thermite reduction

(4) Carbon reduction

The reduction of an oxide by aluminium is called:

(1) Bayer's process

(2) Goldschmidt's aluminothermite process

(3) Hall's process

(4) van Arkel process

The chemical composition of "slag" formed during the smelting process in the extraction of copper is :

(1) $C{u}_2+FeS$                                   

(2) FeSiO₃

(3) CuFeS                                         

(4) $C{u}_{2}S+FeO$

The basic principle of froth floatation is-