Carbon tetrachloride is used for:

Question

Accepted Answer

The correct option is 1:
Carbon tetrachloride ($\text{CCl}\_4$), also historically known as tetrachloromethane, is a potent non-polar organic solvent. Its chemical structure, consisting of a central carbon atom bonded to four chlorine atoms, gives it exceptional dissolving capabilities for other non-polar substances. The fundamental chemical principle "like dissolves like" explains this function perfectly: since grease, fats, and oils are non-polar organic residues, they are readily and effectively dissolved by $\text{CCl}\_4$, which makes it an excellent degreaser. Historically, this property led to its widespread use in industry, in dry cleaning processes, and as a popular spot remover for oily stains in textile and home science applications. Although its use is now heavily restricted globally due to its severe toxicity to humans and its detrimental environmental effects (it is an ozone-depleting substance), its primary and most defining chemical application is dissolving non-polar contaminants, such as removing grease.

The incorrect option is 2:
Clean tarnished metals is an incorrect function for carbon tetrachloride because tarnish is not a grease or oil stain. Tarnish is a form of corrosion, typically a thin layer of metal sulfide or metal oxide that forms on the surface of reactive metals, such as silver or brass, due to chemical reaction with compounds in the air. The removal of tarnish requires either a chemical reduction reaction (which can be done with specialized chemical dips or electrochemical baths) or mechanical action using a mild abrasive and polish. As an organic solvent, carbon tetrachloride is completely unreactive toward these inorganic metal compounds and therefore cannot chemically reverse or remove the tarnish layer.

The incorrect option is 3:
Remove saw dust is an entirely inappropriate and ineffective application for a chemical solvent like carbon tetrachloride. Sawdust is a solid, particulate material made up of tiny pieces of wood, and its removal is a purely mechanical process. Suitable methods for removing sawdust involve physical displacement, such as sweeping, vacuuming, or blowing the particles away with air pressure. Using a volatile, toxic chemical solvent to clean solid particles would not only be wasteful and hazardous but also pointless, as the solvent is designed to dissolve substances, not physically move them.

The incorrect option is 4:
Polish wooden surfaces is incorrect because carbon tetrachloride is a powerful solvent, not a polishing agent. A wood polish is specifically formulated to apply a protective, glossy, and durable layer—often a combination of waxes, oils, or resins—to the surface of the wood. Using a solvent like $\text{CCl}\_4$ on a finished wooden surface would have the damaging effect of stripping away the existing varnish, lacquer, or wax layer. This would leave the surface unprotected, dull, and potentially even bleached or damaged, which is the direct opposite of what is intended by polishing.