---
title: "CFCs in ozone depletion and harmful effects"
subject: "Engineering Chemistry"
chapter: 3
key: "semester_2/engineering_chemistry:cfc-ozone-harmful"
source: https://www.bctengineer.com/q/semester_2/engineering_chemistry/cfc-ozone-harmful
site: BCT Engineering
---

# CFCs in ozone depletion and harmful effects

Engineering Chemistry · Chapter 3: Environmental Chemistry

- Asked in: 2070 Bhadra, 2 marks
- Video: [A Level Chemistry Revision "Chlorofluorocarbons and the Ozone Layer"](https://www.youtube.com/watch?v=GhH77DcEv9M) — Freesciencelessons
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_2/engineering_chemistry/cfc-ozone-harmful
- Whole chapter: https://www.bctengineer.com/md/semester_2/engineering_chemistry/chapter-3

## Question

Write the CFC involved for ozone layer depletion and harmful effects.

## Short answer

CFC-11 (CCl₃F) and CFC-12 (CCl₂F₂) release chlorine atoms under UV radiation, catalytically destroying ozone. Harmful effects include increased UV-B causing skin cancer, cataracts, reduced crop yields, death of phytoplankton, and degradation of plastics and paints.

## Answer

#### CFCs involved
The CFCs mainly responsible are CCl₃F (CFC-11), CCl₂F₂ (CFC-12), and also CCl₂FCClF₂ (CFC-113). In the stratosphere UV breaks them to give chlorine atoms, which destroy ozone catalytically:

CCl₂F₂ + hν → •CClF₂ + Cl•;  Cl• + O₃ → ClO• + O₂;  ClO• + O → Cl• + O₂

#### Harmful effects of ozone depletion
- Increased UV-B reaching the earth causes skin cancer, sunburn, cataract and weakening of the immune system.
- Damages crops and forests, reducing yield.
- Kills phytoplankton and other aquatic organisms, upsetting the marine food chain.
- Degrades plastics and paints; increases ground-level ozone and smog.
- Contributes to global warming (CFCs are greenhouse gases).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Which CFCs are mainly responsible for ozone depletion?
   A. CH4 and CO2
   B. CCl3F (CFC-11), CCl2F2 (CFC-12), CCl2FCClF2 (CFC-113)
   C. NO and NO2
   D. HCl and HF
   Answer: B. These are the key Freons. (Key point: Which CFCs)

2. What is the chain reaction of chlorine with ozone?
   A. Cl. + O2 -> ClO2, then ClO2 -> Cl. + O2
   B. Cl. + O3 -> Cl2 + O2 only
   C. Cl. + O3 -> ClO. + O2, then ClO. + O -> Cl. + O2
   D. Cl. + O3 -> ClO3 which is stable
   Answer: C. Chlorine is regenerated in the second step, so it acts as a catalyst. (Key point: Chain reaction)

3. Which is a harmful effect of increased UV-B due to ozone depletion?
   A. Decreased skin cancer
   B. Increased phytoplankton growth
   C. Higher crop yield
   D. Skin cancer, cataract and a weakened immune system
   Answer: D. More UV-B causes skin cancer, sunburn, cataract and immune suppression and harms crops and plankton. (Key point: UV-B effects)

4. How does ozone depletion affect marine life?
   A. Kills phytoplankton, upsetting the marine food chain
   B. Helps phytoplankton grow faster
   C. It only affects deep-sea fish directly
   D. No effect on aquatic life
   Answer: A. Phytoplankton is the base of the marine food chain. (Key point: Marine impact)

## Related in Engineering Chemistry

- [Photochemistry behind ozone layer depletion](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Aozone-photochemistry) — Engineering Chemistry, chapter 3
- [Short note: Ozone depletion](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Aozone-depletion) — Engineering Chemistry, chapter 3, asked 2×
- [Water pollutants, harmful effects, control measures](https://www.bctengineer.com/question.md?key=semester_2%2Fengineering_chemistry%3Awater-pollutants-effects-measures) — Engineering Chemistry, chapter 3

## Related in other subjects

- [Stratospheric ozone depletion mechanism and effects](https://www.bctengineer.com/question.md?key=semester_7%2Fenvironment_and_pollution_control%3Aozone-depletion-mechanism-effects) — Environment and Pollution Control, chapter 7
- [PN junction built-in potential and depletion layer](https://www.bctengineer.com/question.md?key=semester_3%2Felectrical_engineering_material%3Apn-junction-builtin-depletion) — Electrical Engineering Material, chapter 6, asked 2×
- [Harmful ingredients in brick earth](https://www.bctengineer.com/question.md?key=semester_3%2Fcivil_engineering_materials%3Aharmful-ingredients-brick-earth) — Civil Engineering Materials, chapter 3, asked 3×
- [Built-in potential and depletion in forward bias](https://www.bctengineer.com/question.md?key=semester_3%2Felectrical_engineering_material%3Aforward-bias-depletion) — Electrical Engineering Material, chapter 6