Nickel is purified by thermal decomposition of its:

(1) Hydride

(2) Chloride

(3) Azide

(4) Carbonyl

4M + 8CN^- + 2H₂O + O₂$\to$ 4[M(CN)₂]^- + 4OH^-

2[M(CN)₂]^- + Zn$\to$[Zn(CN)₄]^2- + 2M

The metal M in above-mentioned reaction is:

1. Nickel

2. Silver

3. Copper

4. Mercury

In the metallurgy of copper, the slag is 

1. FeSiO₃

2. CaCO₃

3. CaSiO₃

4. CaO

Galena contains ZnS with PbS. Which of the following is used as depressant to stop ZnS to come with foam?

1. NaCN

2. Aniline

3. Pine Oil

4. H₂O

Vapour phase refining can be carried out in case of 

1. Ni

2. Zr

3. Ti

4. All of these

The extraction of gold and silver involves leaching with CN^- ion. Silver is later recovered by:

1. Liquation

2. Distillation

3. Zone refining

4. Displacement with Zn

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