Most commonly used freon in the industries is

Freon 12

The correct answer is option 1. Freon 12.

Freon 12, or dichlorodifluoromethane \((CCl_2F_2)\), was historically one of the most commonly used freons in industries. It gained popularity due to its favorable properties, including being non-flammable, non-toxic, and having a low boiling point. These properties made it suitable for various industrial applications, particularly as a refrigerant.

In industrial settings, Freon 12 was widely used in refrigeration systems, air conditioning units, and as a propellant in aerosol cans. Its low boiling point allowed it to absorb heat effectively during the refrigeration process and to maintain a constant temperature in air conditioning systems.

However, Freon 12, along with other chlorofluorocarbons (CFCs), became a significant environmental concern due to its role in ozone depletion when released into the atmosphere. As a result, its production and use have been regulated or phased out in many countries under international agreements like the Montreal Protocol.

Despite its declining use due to environmental concerns, Freon 12 remains notable as one of the earliest and most widely used refrigerants in industrial applications.