In a redox reaction: MCQ with Answer and Explanation

Explanation:
The thermite process involves the reduction of a metal oxide by aluminum powder, which is highly exothermic. It is used to extract metals like chromium, manganese, and iron from their oxides (e.g., Cr2O3 + 2Al -> 2Cr + Al2O3). It is also practically used for welding iron railway tracks.

Explanation:
H₂O₂ is a strong oxidizing agent that damages bacterial cell walls, membranes, and essential biomolecules through oxidation, killing microorganisms. It is used as a 3% solution for wound cleaning. The foaming action is due to catalase in tissues breaking it down, releasing O₂. It is not a reducing agent, acid, or dehydrating agent.

Explanation:
Rusting is a chemical change because iron reacts with atmospheric oxygen and moisture to form hydrated iron(III) oxide. This new compound possesses entirely different chemical properties from the original iron. The process involves the formation of new chemical bonds and cannot be easily reversed by simple physical methods.