Under the U.S. Clean Air Act classification of ozone-depleting substances,…
2024
Under the U.S. Clean Air Act classification of ozone-depleting substances, which of the following statements are true?
A. The ozone-depletion potential of Class I substances is generally much greater than that of Class II substances.
B. The ozone-depletion potential of Class II substances is generally much greater than that of Class I substances.
C. All chlorofluorocarbons (CFCs) are Class II ozone-depleting substances.
D. HCFC-21 is a Class II ozone-depleting substance.
E. Class I includes fully halogenated substances such as CFCs.
Choose the correct answer from the options given below:
Answer: A. A, D and E only — Concept: The U.S. Clean Air Act groups ozone-depleting substances into Class I and Class II according to their chemistry and ozone-depletion potential. Class…
- A.
A, D and E only
- B.
B, C and E only
- C.
A, C and D only
- D.
C, D and E only
Show answer & explanation
Correct answer: A
Concept: The U.S. Clean Air Act groups ozone-depleting substances into Class I and Class II according to their chemistry and ozone-depletion potential.
Class I includes higher-ODP substances such as chlorofluorocarbons and other fully halogenated compounds. Class II consists of hydrochlorofluorocarbons, whose hydrogen atom permits faster breakdown in the lower atmosphere and generally gives them lower ODPs.
Application
The claim that Class I substances generally have much greater ozone-depletion potential than Class II substances follows the regulatory distinction.
The reverse comparison is not consistent with that distinction.
The claim that all CFCs are Class II conflicts with the Class I table, which includes CFCs.
HCFC-21 is listed among Class II substances.
Class I includes fully halogenated substances, including CFCs.
Contrast of the offered combinations
A, D and E only retains the three supported statements.
B, C and E only includes the reversed ODP comparison and assigns CFCs to Class II.
A, C and D only assigns CFCs to Class II.
C, D and E only assigns CFCs to Class II and omits the supported relative-ODP statement.
Cross-check
The EPA Class I table places CFCs among Class I substances, while the Class II table lists HCFC-21; this independently confirms the classification used above.
Result
Therefore, the true statements are A, D and E only.