CFC Chlorofluorocarbon Properties & Environmental Impact 3 — Questions and Answers
Question 1: The Montreal Protocol was signed in 1987 primarily to address which environmental problem?
- Acid rain from sulfur emissions
- Stratospheric ozone depletion by CFCs and halons (Correct answer)
- Greenhouse gas emissions causing climate change
- Heavy metal contamination of waterways
Correct answer: Stratospheric ozone depletion by CFCs and halons
The Montreal Protocol on Substances that Deplete the Ozone Layer was negotiated in response to scientific evidence that CFCs and halons were destroying the stratospheric ozone layer.
Question 2: R-12, one of the most widely used CFCs, has the chemical formula:
- CCl₃F
- CCl₂F₂ (Correct answer)
- CClF₃
- C₂Cl₂F₄
Correct answer: CCl₂F₂
R-12 (dichlorodifluoromethane) has the formula CCl₂F₂, featuring two chlorine atoms and two fluorine atoms on a single carbon, giving it high stability and ODP of 1.0.
Question 3: In the context of CFC refrigerants, what does the term 'critical temperature' refer to?
- The temperature at which the refrigerant begins to decompose
- The temperature above which the refrigerant cannot exist as a liquid regardless of pressure (Correct answer)
- The minimum temperature achievable in a refrigeration cycle
- The temperature at which ozone depletion begins
Correct answer: The temperature above which the refrigerant cannot exist as a liquid regardless of pressure
Critical temperature is the temperature above which a substance cannot be liquefied by pressure alone, which determines the operating limits of refrigeration systems using that refrigerant.
Question 4: Which CFC compound was widely used as a blowing agent in foam insulation before being phased out?
- R-11 (CFC-11) (Correct answer)
- R-22 (HCFC-22)
- R-134a (HFC-134a)
- R-410A
Correct answer: R-11 (CFC-11)
CFC-11 (trichlorofluoromethane) was extensively used as a blowing agent for rigid polyurethane foam insulation due to its low boiling point and insulating properties.
Question 5: What is the approximate atmospheric lifetime of CFC-12 (R-12)?
- 5–10 years
- 25–30 years
- 100 years (Correct answer)
- 500 years
Correct answer: 100 years
CFC-12 has an atmospheric lifetime of approximately 100 years, meaning emissions today will continue depleting the ozone layer for a century.
Question 6: Which region of the world first showed dramatic evidence of ozone depletion attributed to CFCs?
- Arctic Circle
- Antarctic (South Pole) (Correct answer)
- Equatorial Pacific
- Saharan Africa
Correct answer: Antarctic (South Pole)
The Antarctic ozone hole was first reported by British scientists in 1985, showing severe seasonal depletion linked to polar stratospheric clouds that catalyze CFC-driven ozone destruction.
Question 7: Under the Clean Air Act Section 608, technicians are prohibited from intentionally releasing CFCs into the atmosphere during what activities?
- Only during system installation
- Maintenance, service, repair, and disposal of appliances (Correct answer)
- Only during disposal of equipment
- Transportation of refrigerant cylinders
Correct answer: Maintenance, service, repair, and disposal of appliances
Section 608 of the Clean Air Act prohibits the knowing venting of CFCs and HCFCs during maintenance, service, repair, or disposal of refrigeration and air-conditioning equipment.
CFC Chlorofluorocarbon Properties & Environmental Impact 3
The Montreal Protocol was signed in 1987 primarily to address which environmental problem?