Radioactive isotope Cobalt-60 is used for: MCQ with Answer and Explanation

Explanation:
Refining is the final step in metallurgy to obtain pure metal. Poling is used for copper to remove oxide impurities. Liquation separates low-melting metals (like tin) from high-melting impurities. Zone refining is used for producing ultra-pure semiconductors (like Si, Ge) based on the principle that impurities are more soluble in the molten state.

Explanation:
Nylon-6,6 is a condensation polymer formed by reaction between hexamethylenediamine and adipic acid, with elimination of water molecules. Polythene, Teflon, and PVC are addition polymers where monomers add without loss of small molecules. Condensation polymers often have amide or ester linkages. Another example is polyester (terylene). Nylon is a polyamide, known for strength and elasticity.

Explanation:
Hydrochloric acid (HCl) is commonly used for pickling (cleaning) steel to remove rust and scale (iron oxides) before further processing like galvanizing or plating. Reaction: Fe₂O₃ + 6HCl → 2FeCl₃ + 3H₂O. Sulfuric acid is also used. Nitric acid is an oxidizer and would passivate some metals. Acetic acid is too weak.