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

Match items of Column I with the items of Column II and assign the correct code.
        Column l                                                                    Column II
A. Cyanide process                                                            1. Ultrapure Ge
B. Froth floatation process                                                 2. Dressing of ZnS
C. Electrolytic reduction                                                      3. Extraction of Al
D. Zone refining                                                                  4. Extraction of Au
                                                                                            5. Purification of Ni
Codes
      A  B  C  D
(a)  2  3  1  5
(b)  1  2  3  4
(c)  3  4  5  1
(d)  4  2  3  1

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

During extraction, copper is obtained by the reduction of cupric oxide with:

1. Cu₂S

2. SO₂

3. FeS

4. CO

A pair of metals among the following that can be purified by the van Arkel method are:

1. Zr,  and Ti

2. Ag, and Au

3. Ni,  and Fe

4. Ga, and In

Sulphide ores of metals are usually concentrated by Froth Flotation process. Which one of the following sulphide ores offers and exception and is concentrated by chemical leaching?

Considering Ellingham diagram, which of the following metals can be used to reduce alumina?

1. Fe

2. Zn

3. Mg

4. Cu

"Metals are usually not found as nitrates in their ores". Out of the following two (I and II) reasons which is/are true for the above observation? 

Roasting of sulphides gives the gas X as a by-product. This is a colourless gas with a choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain. Its aqueous solution is acidic and  acts as an oxidizing agent and its acid has never been isolated. The gas X is:

1. SO₂

2. CO₂

3. SO₃

4. H₂S

Which one of the following is a mineral of iron?

1. Malachite

2. Cassiterite

3. Pyrolusite

4. Magnetite