Chemistry Q125 – AP-EAMCET 2026

Home Chemistry Chemical BondingQuestion #207

The increasing order of N – N bond length of

N_{2} O (A)

N_{2} O_{3} (B)

N_{2} O_{4} (C)

Clue 1 of 3: Bond Order and Bond Length

The length of a chemical bond is inversely proportional to its bond order. Higher bond order means a stronger and shorter bond.

🧠 Full Solution Path

Step 1: Determine Lewis Structures and N-N Bond Orders✦ Active

First, we determine the Lewis structures and analyze the N-N bond character for each compound:

A) $N_{2} O$ (Nitrous Oxide): The N-N bond in $N_{2} O$ exhibits resonance. The major resonance structures are $: N \equiv N - \ddot{O} :^{-}$ and $: \ddot{N} = N = \ddot{O} :$ . The N-N bond has a bond order between 2 and 3, typically considered around 2.5, indicating significant triple bond character. Its experimental bond length is approximately $1.128 Å$ .

B) $N_{2} O_{3}$ (Dinitrogen Trioxide): The N-N bond in $N_{2} O_{3}$ is a single bond, connecting an $N O$ group to an $N O_{2}$ group ( $O = N - N (O) = O$ ). Its experimental bond length is approximately $1.864 Å$ .

C) $N_{2} O_{4}$ (Dinitrogen Tetroxide): The N-N bond in $N_{2} O_{4}$ is a single bond, connecting two $N O_{2}$ groups ( $O_{2} N - N O_{2}$ ). Its experimental bond length is approximately $1.75 Å$ .

💡 Teacher's Secret Hint

Remember that bond length is inversely proportional to bond order. A triple bond is shorter than a double bond, which is shorter than a single bond.

Step 2: Compare N-N Bond Lengths○ Expand

Now, we compare the experimental N-N bond lengths:

- For $N_{2} O$ (A): $1.128 Å$ (due to high bond order)

- For $N_{2} O_{3}$ (B): $1.864 Å$ (single bond)

- For $N_{2} O_{4}$ (C): $1.75 Å$ (single bond, but weaker and slightly shorter than in $N_{2} O_{3}$ due to different electronic environments and hybridization)

💡 Teacher's Secret Hint

While both $N_{2} O_{3}$ and $N_{2} O_{4}$ have N-N single bonds, their exact lengths can differ due to factors like hybridization and resonance in the attached groups. For these specific molecules, $N_{2} O_{3}$ has a longer N-N bond than $N_{2} O_{4}$ .

Step 3: Order Compounds by Increasing Bond Length○ Expand

Arranging these bond lengths in increasing order:

$1.128 Å (N_{2} O) < 1.75 Å (N_{2} O_{4}) < 1.864 Å (N_{2} O_{3})$

Therefore, the increasing order of N-N bond length is $A < C < B$ .

💡 Teacher's Secret Hint

Always double-check the question to ensure you are ordering in the correct direction (increasing or decreasing).

Step 4: Select the Correct Option○ Expand

The order $A, C, B$ corresponds to option 1.

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Chemistry Question 125 – AP-EAMCET 2026

Clue 1 of 3: Bond Order and Bond Length

🧠 Full Solution Path