Which of the following is a method of refining (purification) of metals? MCQ with Answer and Explanation

Explanation:
Mercury (Hg) is the only metal that is liquid at room temperature. Gallium and cesium melt slightly above room temperature. Sodium is solid but soft. Zinc and aluminium are solids. Mercury is used in thermometers and barometers.

Explanation:
Borosilicate glass (e.g., Pyrex) contains boron trioxide (B₂O₃) along with silica, giving it low coefficient of thermal expansion, thus resistant to cracking under temperature changes. Soda-lime glass is ordinary glass, used for bottles, windows. Lead crystal has high refractive index for decorative items. Quartz glass (pure SiO₂) has very high melting point but is expensive. Borosilicate is ideal for beakers, test tubes.

Explanation:
Fajan's rules state that covalent character in an ionic bond increases with greater polarizing power of the cation and greater polarizability of the anion. A small cation has high charge density (high polarizing power), and a large anion has loosely held outer electrons (high polarizability), favoring covalency.