Which metal is obtained by self reduction process?

All of these

The correct answer is option 4. All of these.

Self-reduction is a process where certain metals with low electropositivity (low tendency to lose electrons and form cations) can be reduced from their oxides or sulfides without the need for an external reducing agent like carbon or hydrogen.

Metals like copper (Cu), lead (Pb), and mercury (Hg) all fall under this category. They can be obtained through self-reduction under specific conditions.

Let us see some examples:

Copper (Cu): In some copper extraction methods, roasting of copper sulfide ores (like \(CuFeS_2\)) can lead to partial self-reduction. The copper sulfide reacts with the copper oxide formed during roasting to produce metallic copper.

Lead (Pb): Galena \((PbS)\), the main lead ore, can undergo self-reduction at high temperatures. Lead sulfide decomposes to yield metallic lead and sulfur dioxide gas.

Mercury (Hg): Cinnabar \((HgS)\), the primary mercury ore, can also exhibit self-reduction behavior when heated. Mercury sulfide breaks down to release elemental mercury and sulfur vapors.

Important Note:

While self-reduction can occur for these metals, it's not always the sole method for their extraction. Other processes like electrolysis or reduction using external agents might be employed depending on the specific ore and desired product characteristics.