"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

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

1. ${\mathrm{Al}}_2{\mathrm{O}}_3+\mathrm{HF}+{\mathrm{NaAlF}}_4$

2. ${\mathrm{Al}}_2{\mathrm{O}}_3+{\mathrm{CaF}}_2+{\mathrm{NaAlF}}_4$

3. ${\mathrm{Al}}_2{\mathrm{O}}_3+{\mathrm{Na}}_3{\mathrm{AlF}}_6+{\mathrm{CaF}}_2$

4. ${\mathrm{Al}}_2{\mathrm{O}}_3+\mathrm{KF}+{\mathrm{Na}}_3{\mathrm{AlF}}_6$

Which one of the following is a mineral of iron?

1. Malachite

2. Cassiterite

3. Pyrolusite

4. Magnetite

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

1. Copper(l) sulphide (Cu₂S)

2. Sulphur dioxide (SO₂)

3. Iron Sulphide (FeS)

4. Carbon monoxide (CO)

An interstitial compound among the following is:

1. Invar

2. Steel

3. Bell metal

4. Bronze

Which of the following elements is present as an impurity to the maximum extent in the pig Iron?
1. Carbon
2. Silicon
3. Phosphorus
4. Manganese

A pair of metals that can be purified by van Arkel method is:

1. Zr and Ti

2. Ag and Au

3. Ni and Fe

4. Ga and In

The following reactions take place in the blast furnace in the preparation of impure iron.
Identify the reaction pertaining to the formation of the slag.

1. 2C(s) + O₂(g) → 2CO (g)
2. Fe₂O₃(s) + 3CO (g) → 2Fe(l) + 3CO₂(g)
3. CaCO₃(s) → CaO(s) + CO₂(g)
4. CaO(s) + SiO₂(s) → CaSiO₃(s)