Which of the following substances has the least Ozone Depleting Potential?
Hydro chlorofluorocarbons
Ozone Depleting Potential (ODP) measures how strongly a substance destroys stratospheric ozone, relative to CFC-11 which is taken as 1. Chlorofluorocarbons have an ODP of about 1; carbon tetrachloride is around 1.1; and halons are the worst of all (ODP roughly 3–10) because the bromine they carry destroys ozone far more efficiently than chlorine.
Hydrochlorofluorocarbons (HCFCs) contain hydrogen atoms, which make the molecule break down partly in the lower atmosphere (troposphere) before it can reach the ozone layer. As a result their ODP is very small — roughly 0.01 to 0.1. Because far less chlorine actually reaches the stratosphere, HCFCs have the least ozone-depleting potential, which is why they were adopted as interim substitutes for CFCs under the Montreal Protocol.
The other substances named all have ODP near or well above 1, so they deplete much more ozone.
Takeaway: adding hydrogen to the molecule, as in HCFCs, sharply lowers its ozone-depleting potential.
Correct answer: Hydro chlorofluorocarbons.
Similar Questions
Assertion (A): High concentration of ozone in the lower troposphere is desirable.
Reason (R): Ozone present in the atmosphere protects the living organisms on the surface of earth from the harmful ultra-violet radiation of the sun.
Choose the correct answer from the options given below:Montreal protocol was signed in order to address which of the following environmental issues?
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: Despite the fact that Chloro Fluoro Carbons(CFCs) are evenly distributed over the globe, the Ozone depletion is significantly pronounced over the south pole.
Reason R: The presence of ice crystals over the south pole makes chlorine to oxygen bonding tougher.
In the light of the above statements, choose the most appropriate answer from the options given below.
Important Questions from Ozone Layer Depletion
- Which of the following is a catalytically inactive (or reservoir) molecule containing chlorine in stratosphere?
- Choose the correct statement(s)
A. O$_3$ in stratosphere is not completely effective in shielding us from UV-B
B. UV-A is biologically least harmful.
C. Chapman mechanism deals with only O$_3$ formation in stratosphere.
D. Sunscreen lotions either reflect or absorb or scatter UV-B and UV-A
E. UV-B helps in dissociation of O$_3$ molecule in stratosphere.
Choose the correct answer from the options given below. Ozone layer depletion is a major phenomenon in :
- With regard to ozone depletion over Antarctica, select the false statement :
- Atmospheric life times of CFCs is typically in the range :
