Which of the following is know as Freon-12:

$CCl_2F_2$

The correct answer is Option (4) → $CCl_2F_2$.

Freon-12 is the trade name for dichlorodifluoromethane \((CCl_2F_2)\). It is one of the most common chlorofluorocarbons (CFCs) that was widely used as a refrigerant and as a propellant in aerosol sprays. However, due to its harmful effects on the ozone layer, its production and use have been largely phased out under the Montreal Protocol.

Properties of Freon-12:

Chemical formula: \(CCl_2F_2\)

Structure: It contains two chlorine atoms and two fluorine atoms attached to a single carbon atom.

Uses: Primarily used as a refrigerant in air conditioning systems and refrigerators, and as a propellant in aerosol sprays.

Environmental impact: Freon-12 contributes to the depletion of the ozone layer because the chlorine atoms in CFCs can catalyze the breakdown of ozone \((O_3)\) in the upper atmosphere.

Incorrect Options:

\(COCl_2\) (Phosgene): A toxic gas used in chemical warfare and as an industrial reagent.

\(CHCl_3\) (Chloroform): A chemical used as a solvent and in the past as an anesthetic.

\(CH_2Cl_2\) (Dichloromethane): A solvent widely used in paint removers and chemical processes.

Thus, \(CCl_2F_2\) is known as Freon-12.