What happens when a ketone is treated with amalgamated zinc (Hg-Zn) and concentrated hydrochloric acid? 

Alkane is formed

The correct answer is option 1. Alkane is formed.

When a ketone is treated with amalgamated zinc \((Hg-Zn)\) and concentrated hydrochloric acid \((HCl)\), a reduction reaction occurs known as the Clemmensen reduction. Here is what happens: Alkane is formed

Clemmensen Reduction:

Amalgamated zinc \((Hg-Zn)\) in the presence of concentrated hydrochloric acid \((HCl)\) reduces ketones to alkanes.

This reduction is a powerful method for converting ketones into alkanes under acidic conditions.

The zinc amalgam acts as a reducing agent, providing electrons to the carbonyl carbon, leading to the formation of a carbanion intermediate.

The acidic conditions help in protonating the oxygen of the intermediate, leading to the elimination of water (dehydration), followed by further reduction to form the corresponding alkane.

Therefore, when a ketone is treated with amalgamated zinc \((Hg-Zn)\) and concentrated hydrochloric acid, the main product formed is an alkane.