---
title: "In a spectroscopy experiment, a student supplies energy to dissociate gaseous \\(\\text{H}_2\\). Some of the resulting hydrogen atoms later recombine. To isolate the energy associated with the bond, the student represents the changes below and compares all species at the same temperature.  | Process | Isolated bond change | |———|———————-| | 1 | \\(\\text{H}_2\\text{(g)} \\rightarrow 2\\text{H(g)}\\) | | 2 | \\(2\\text{H(g)} \\rightarrow \\text{H}_2\\text{(g)}\\) |  No other bonds are broken or formed. Which statement correctly identifies the signs of \\(\\Delta H_1\\) and \\(\\Delta H_2\\) and explains them using a particle-attraction model?"
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url: "https://nerd-notes.com/ubq/119440/"
date_modified: "2026-08-19T12:40:23+00:00"
---

# In a spectroscopy experiment, a student supplies energy to dissociate gaseous \(\text{H}_2\). Some of the resulting hydrogen atoms later recombine. To isolate the energy associated with the bond, the student represents the changes below and compares all species at the same temperature.

| Process | Isolated bond change |
|———|———————-|
| 1 | \(\text{H}_2\text{(g)} \rightarrow 2\text{H(g)}\) |
| 2 | \(2\text{H(g)} \rightarrow \text{H}_2\text{(g)}\) |

No other bonds are broken or formed. Which statement correctly identifies the signs of \(\Delta H_1\) and \(\Delta H_2\) and explains them using a particle-attraction model?

In a spectroscopy experiment, a student supplies energy to dissociate gaseous \(\text{H}_2\). Some of the resulting hydrogen atoms later recombine. To isolate the energy associated with the bond, the student represents the changes below and compares all species at the same temperature.

| Process | Isolated bond change |
|---------|----------------------|
| 1 | \(\text{H}_2\text{(g)} \rightarrow 2\text{H(g)}\) |
| 2 | \(2\text{H(g)} \rightarrow \text{H}_2\text{(g)}\) |

No other bonds are broken or formed. Which statement correctly identifies the signs of \(\Delta H_1\) and \(\Delta H_2\) and explains them using a particle-attraction model?

- **A.** \(\Delta H_1<0\) and \(\Delta H_2>0\), because eliminating the attraction between the nuclei and the shared electron density places the separated atoms at lower potential energy than the bonded molecule.
- **B.** \(\Delta H_1<0\) and \(\Delta H_2>0\), because the \(\text{H-H}\) bond stores energy that is released when the bond breaks and must be supplied again when the bond forms.
- **C.** \(\Delta H_1>0\) and \(\Delta H_2<0\), because dissociation increases the number of particles and bond formation decreases the number of particles, directly determining the direction of heat transfer.
- **D.** \(\Delta H_1>0\) and \(\Delta H_2<0\), because pulling the bonded atoms apart requires energy to overcome stabilizing attractions, whereas bond formation lowers the system's potential energy and releases energy.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119440/*