Given below are two statements : Statement (I) : Experimentally determined oxygen-oxygen bond lengths in the O_3 are found to be same and the bond length is greater than that of a O=O (double bond) but less than that of a single (O-O) bond. Statement (II) : The strong lone pair-lone pair repulsion between oxygen atoms is solely responsible for the fact that the bond length in ozone is smaller than that of a double bond (O=O) but more than that of a single bond (O-O) . In the light of the above statements, choose the correct answer from the options given below :

Statement I is true but Statement II is false

Statement I is false but Statement II is true

Both Statement I and Statement II are true

Both Statement I and Statement II are false

Chemical Bonding and Molecular Structure PYQ — JEE Main 2025 · 24 Jan · Shift 2 · Q16 with Solution

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Correct answer: C

Analyze Statement (I)

Ozone, $\mathrm{O_3}$ , is a resonance hybrid of the structures:

\mathrm{O=O-O} \leftrightarrow \mathrm{O-O=O}

Because of resonance:

both $\mathrm{O-O}$ bonds become equivalent,
each bond has bond order:

\text{Bond order} = \frac{2+1}{2} = 1.5

Hence, the two experimentally observed $\mathrm{O-O}$ bond lengths in ozone are the same.

Also, a bond with bond order $1.5$ should have length:

greater than a double bond length,
less than a single bond length.

So Statement (I) is true.

Analyze Statement (II)

Statement (II) says that strong lone pair-lone pair repulsion is solely responsible for the bond length behavior in ozone.

This is incorrect for two reasons:

The primary reason for equal intermediate bond lengths in ozone is resonance / delocalization.
Also, the statement says the bond length in ozone is smaller than that of a double bond and more than that of a single bond, which is opposite to the actual trend.

Actual trend is:

\text{double bond length} < \text{ozone bond length} < \text{single bond length}

Thus Statement (II) is false.

Evaluate options

A: Statement I false, Statement II true $\to$ incorrect
B: Both true $\to$ incorrect
C: Statement I true, Statement II false $\to$ correct
D: Both false $\to$ incorrect

Final Answer

The correct option is:

\boxed{\text{C}}

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View written solutionFree

Correct answer: C

Analyze Statement (I)

Ozone, $\mathrm{O_3}$ , is a resonance hybrid of the structures:

\mathrm{O=O-O} \leftrightarrow \mathrm{O-O=O}

Because of resonance:

both $\mathrm{O-O}$ bonds become equivalent,
each bond has bond order:

\text{Bond order} = \frac{2+1}{2} = 1.5

Hence, the two experimentally observed $\mathrm{O-O}$ bond lengths in ozone are the same.

Also, a bond with bond order $1.5$ should have length:

greater than a double bond length,
less than a single bond length.

So Statement (I) is true.

Analyze Statement (II)

Statement (II) says that strong lone pair-lone pair repulsion is solely responsible for the bond length behavior in ozone.

This is incorrect for two reasons:

The primary reason for equal intermediate bond lengths in ozone is resonance / delocalization.
Also, the statement says the bond length in ozone is smaller than that of a double bond and more than that of a single bond, which is opposite to the actual trend.

Actual trend is:

\text{double bond length} < \text{ozone bond length} < \text{single bond length}

Thus Statement (II) is false.

Evaluate options

A: Statement I false, Statement II true $\to$ incorrect
B: Both true $\to$ incorrect
C: Statement I true, Statement II false $\to$ correct
D: Both false $\to$ incorrect

Final Answer

The correct option is:

\boxed{\text{C}}

Chemical Bonding and Molecular Structure question

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