---
title: "A student investigating nitrogen-rich polymer precursors compares representative data for three nitrogen-nitrogen bonds.  | Bond | Bond dissociation energy (kJ/mol) | Equilibrium bond length (pm) | |——|————————————|——————————| | \\(\\text{N}-\\text{N}\\) | \\(160\\) | \\(145\\) | | \\(\\text{N}=\\text{N}\\) | \\(420\\) | \\(125\\) | | \\(\\text{N}\\equiv\\text{N}\\) | \\(940\\) | \\(110\\) |  The vibrational force constant, \\(k\\), measures a bond’s resistance to small changes in length and corresponds to the steepness of its potential-energy well near the equilibrium bond length. Which choice correctly ranks the force constants from greatest to least and provides the best justification?"
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url: "https://nerd-notes.com/ubq/119484/"
date_modified: "2026-08-19T12:40:41+00:00"
---

# A student investigating nitrogen-rich polymer precursors compares representative data for three nitrogen-nitrogen bonds.

| Bond | Bond dissociation energy (kJ/mol) | Equilibrium bond length (pm) |
|——|————————————|——————————|
| \(\text{N}-\text{N}\) | \(160\) | \(145\) |
| \(\text{N}=\text{N}\) | \(420\) | \(125\) |
| \(\text{N}\equiv\text{N}\) | \(940\) | \(110\) |

The vibrational force constant, \(k\), measures a bond’s resistance to small changes in length and corresponds to the steepness of its potential-energy well near the equilibrium bond length. Which choice correctly ranks the force constants from greatest to least and provides the best justification?

A student investigating nitrogen-rich polymer precursors compares representative data for three nitrogen-nitrogen bonds.

| Bond | Bond dissociation energy (kJ/mol) | Equilibrium bond length (pm) |
|------|------------------------------------|------------------------------|
| \(\text{N}-\text{N}\) | \(160\) | \(145\) |
| \(\text{N}=\text{N}\) | \(420\) | \(125\) |
| \(\text{N}\equiv\text{N}\) | \(940\) | \(110\) |

The vibrational force constant, \(k\), measures a bond’s resistance to small changes in length and corresponds to the steepness of its potential-energy well near the equilibrium bond length. Which choice correctly ranks the force constants from greatest to least and provides the best justification?

- **A.** \(k_{\text{N}-\text{N}} > k_{\text{N}=\text{N}} > k_{\text{N}\equiv\text{N}}\), because a longer bond can be stretched through a greater distance before dissociation and therefore has a larger force constant.
- **B.** \(k_{\text{N}=\text{N}} > k_{\text{N}\equiv\text{N}} > k_{\text{N}-\text{N}}\), because adding the first \(\pi\) bond increases stiffness, whereas adding a second \(\pi\) bond decreases stiffness by making the bonding electron density more diffuse.
- **C.** \(k_{\text{N}\equiv\text{N}} > k_{\text{N}-\text{N}} > k_{\text{N}=\text{N}}\), because the triple bond has the greatest bond energy, but the single bond is stiffer than the double bond because it has a greater equilibrium bond length.
- **D.** \(k_{\text{N}\equiv\text{N}} > k_{\text{N}=\text{N}} > k_{\text{N}-\text{N}}\), because increasing bond order increases the shared electron density between the nuclei, producing shorter, stronger bonds with more steeply curved potential-energy wells.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119484/*