Dichlorodifluoromethane (CCl2F2) is a chlorofluorocarbon refrigerant. What is its well known common trade name?

Introduction / Context:
Many industrial chemicals are sold under trade names that become widely used in science and engineering. Dichlorodifluoromethane, with formula CCl2F2, is a chlorofluorocarbon that was once very common in refrigeration and air conditioning systems. It is better known to students and technicians by its common trade name. Recognising this name helps in understanding discussions about refrigerants and environmental issues such as ozone layer depletion.

Given Data / Assumptions:

• The compound in question is dichlorodifluoromethane, formula CCl2F2.
• It is a refrigerant gas and belongs to the chlorofluorocarbon (CFC) family.
• Options include names of minerals and industrial products such as galena, gypsum, borax, and Teflon, as well as a refrigerant trade name.
• We assume standard usage of these common names in school chemistry.

Concept / Approach:
The family of chlorofluorocarbon refrigerants was marketed under the trade name Freon. Specific members of this family are numbered, and dichlorodifluoromethane (CCl2F2) is known as Freon-12. Galena is lead sulphide ore, gypsum is calcium sulphate dihydrate, borax is hydrated sodium borate, and Teflon is polytetrafluoroethylene. None of these are refrigerant gases of the CCl2F2 type. Therefore, the correct common name for dichlorodifluoromethane is Freon-12, usually shortened to Freon in general statements.

Step-by-Step Solution:
Step 1: Identify the chemical as dichlorodifluoromethane, a molecule with one carbon, two chlorine, and two fluorine atoms. Step 2: Recall that this type of molecule belongs to the chlorofluorocarbons, which were widely used as refrigerants and propellants. Step 3: Remember that DuPont and other companies sold these compounds under the trade name Freon, with different numbers for different formulations. Step 4: Note that CCl2F2 corresponds to Freon-12 in this numbering system. Step 5: Select the option that clearly names Freon-12 as the common trade name.

Verification / Alternative check:
Older textbooks and technical manuals on refrigeration refer to CCl2F2 as R-12 or Freon-12. Environmental discussions on CFCs also mention Freon as a major class of ozone depleting substances, with dichlorodifluoromethane as a typical example. In contrast, mineralogy texts define galena as PbS, gypsum as CaSO4·2H2O, and borax as Na2B4O7·10H2O. Polymer chemistry texts identify Teflon as a solid fluoropolymer, not a gaseous refrigerant. These references confirm that Freon-12 is the correct trade name for CCl2F2.

Why Other Options Are Wrong:
Galena is an ore of lead, chemically lead sulphide, and has nothing to do with refrigerant gases. Gypsum is a hydrated calcium sulphate used in plaster and cement. Borax is a sodium borate used in detergents and glass manufacture. Teflon is a solid polymer used as a non stick coating and in electrical insulation. None of these substances are dichlorodifluoromethane or share its role as a traditional refrigerant gas.

Common Pitfalls:
Some learners may simply pick a familiar sounding chemical like Teflon without checking whether it is a gas or solid, or whether it is used as a refrigerant. Others may not recognise the connection between chlorofluorocarbons and the Freon trade name. To avoid such errors, remember that many older refrigerants and aerosol propellants labelled as CFCs were marketed as Freon, and CCl2F2 specifically is Freon-12.

Final Answer:
The common trade name of dichlorodifluoromethane (CCl2F2) is Freon-12, commonly referred to as Freon.