Given below are two statements :
Statement I Chlorofluoro carbons break down by radiation in the vis

Q: Why doesn't visible light break down CFCs?

Visible light photons do not have sufficient energy to overcome the bond dissociation energy of the carbon-chlorine bonds in CFCs. Only higher-energy UV radiation, found in the stratosphere, can break these bonds.

Q: What is the difference between chlorine gas and a chlorine free radical?

Chlorine gas ($Cl_2$) is a stable diatomic molecule. A chlorine free radical ($\dot{C}l$) is a single chlorine atom with an unpaired electron, making it extremely reactive and capable of initiating chain reactions that destroy ozone.

Q: How does NO reach the stratosphere to react with ozone?

Nitric oxide (NO) can be introduced into the stratosphere directly by the exhaust of supersonic transport aircraft flying at high altitudes, or it can be formed from the breakdown of nitrous oxide ($N_2O$) which diffuses up from the troposphere.

Q: Is nitrogen dioxide ($NO_2$) harmful to the ozone layer?

Yes, $NO_2$ can further react with atomic oxygen to regenerate NO, continuing the catalytic cycle of ozone destruction: $NO_2 + O \rightarrow NO + O_2$.

Q: Why are these specific reactions so important for the environment?

These reactions describe the mechanisms of ozone depletion. The ozone layer protects life on Earth by absorbing harmful UV radiation. Understanding these reactions led to global agreements like the Montreal Protocol to phase out CFCs.

Question

Given below are two statements :
Statement I Chlorofluoro carbons break down by radiation in the visible energy region and release chlorine gas in the atmosphere which then reacts with stratospheric ozone.
Statement II Atmospheric ozone reacts with nitric oxide to give nitrogen and oxygen gases, which add to the atmosphere.
For the above statements choose the correct answer from the options given below :

Options:

(A) Statement I is incorrect but statement II is true

(B) Both statement I and II are false

(C) Statement I is correct but statement II is false

(D) Both statement I and II are correct

Sigma Percentile · Accepted Answer

### Analyzing the Setup
We are given two statements regarding atmospheric chemistry, specifically focusing on the depletion of the ozone layer and the reactions involved. Our goal is to evaluate the factual accuracy of each statement based on our knowledge of environmental chemistry.

### Evaluating Statement I
The first statement claims that chlorofluorocarbons (CFCs) break down by radiation in the visible energy region and release chlorine gas in the atmosphere, which then reacts with stratospheric ozone.

Let's break this down. CFCs are highly stable compounds in the lower atmosphere (troposphere). They do not break down under visible light because visible light does not carry enough energy to break the strong carbon-chlorine bonds. Instead, they migrate to the stratosphere where they are exposed to high-energy **ultraviolet (UV) radiation**.

When a CFC molecule, such as $CF_2Cl_2$, absorbs UV radiation, it undergoes homolytic cleavage to form highly reactive free radicals, not stable chlorine gas ($Cl_2$). The reaction is:
$$CF_2Cl_2(g) \xrightarrow{UV} \dot{C}l(g) + \dot{C}F_2Cl(g)$$

Because the statement incorrectly identifies both the type of radiation (visible instead of UV) and the product (chlorine gas instead of chlorine free radicals), **Statement I is completely false**.

### Evaluating Statement II
The second statement asserts that atmospheric ozone reacts with nitric oxide (NO) to give nitrogen ($N_2$) and oxygen ($O_2$) gases.

Nitric oxide is indeed a significant ozone-depleting substance. However, we must look closely at the chemical reaction. When NO reacts with ozone ($O_3$), it strips an oxygen atom from the ozone molecule, forming **nitrogen dioxide** ($NO_2$) and oxygen gas ($O_2$). The balanced chemical equation is:
$$NO(g) + O_3(g) \rightarrow NO_2(g) + O_2(g)$$

The statement claims that nitrogen gas ($N_2$) is produced, which is factually incorrect. Therefore, **Statement II is also false**.

### Final Conclusion
Since both statements contain critical factual errors regarding the chemical species and conditions involved in atmospheric reactions, we conclude that both Statement I and Statement II are false. This makes option (b) the correct choice.

Select Answer:

Visualized Solution

$S t a t e m e n t I A na l y s i s$

$C F C B r e ak d o w n R e a c t i o n$

$C o n c l u s i o n f or S t a t e m e n t I$

$S t a t e m e n t I I A na l y s i s$

$R e a c t i o n o f N O w i t h O z o n e$

$C o n c l u s i o n f or S t a t e m e n t I I$

$F ina l A n s w er$

The Sigma Insight: Atmospheric Pollution

Analyzing the Setup We are given two statements regarding atmospheric chemistry, specifically focusing on the depletion of the ozone layer and the reactions involved

Evaluating Statement I

Evaluating Statement II

Final Conclusion Since both statements contain critical factual errors regarding the chemical species and conditions involved in atmospheric reactions, we conclude that both Statement I and Statement II are false

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