---
title: "The potential energy of a two-atom system as a function of internuclear distance during the interaction of two chlorine atoms is represented in the graph below.  \\[ \\text{Cl}_2(g) \\rightarrow 2\\,\\text{Cl}(g) \\]  Which of the following best describes the enthalpy change, \\(\\Delta H^\\circ\\), for the reaction represented above and provides the correct physical justification?"
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url: "https://nerd-notes.com/ubq/119775/"
date_modified: "2026-08-21T08:12:18+00:00"
---

# The potential energy of a two-atom system as a function of internuclear distance during the interaction of two chlorine atoms is represented in the graph below.

\[ \text{Cl}_2(g) \rightarrow 2\,\text{Cl}(g) \]

Which of the following best describes the enthalpy change, \(\Delta H^\circ\), for the reaction represented above and provides the correct physical justification?

The potential energy of a two-atom system as a function of internuclear distance during the interaction of two chlorine atoms is represented in the graph below.

\[ \text{Cl}_2(g) \rightarrow 2\,\text{Cl}(g) \]

Which of the following best describes the enthalpy change, \(\Delta H^\circ\), for the reaction represented above and provides the correct physical justification?

![A 2D line graph displays potential energy on the vertical axis and internuclear distance on the horizontal axis without numerical gridlines. A horizontal dashed line represents a potential energy of zero across the entire horizontal span. A single continuous solid black curve starts at a high positive potential energy at the far left near the vertical axis, curves steeply downward crossing below the dashed zero line, reaches a single rounded minimum well labeled \(-E_{\text{bond}}\) at an internuclear distance labeled \(r_0\), and then rises smoothly to the right, asymptotically approaching the dashed line from below at large internuclear distances. A dashed vertical guideline drops from the well minimum to the horizontal axis at \(r_0\). No other particles, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787299938-4q7Tfq.jpg)

- **A.** The process is exothermic (\(\Delta H^\circ < 0\)) because energy stored in the covalent bond is released to the surroundings as the shared electrons return to the individual chlorine atoms.
- **B.** The process is endothermic (\(\Delta H^\circ > 0\)) because energy must be absorbed to overcome the net electrostatic attractions between the shared electrons and the chlorine nuclei, moving the system from the potential energy well to a higher potential energy state.
- **C.** The process is endothermic (\(\Delta H^\circ > 0\)) because energy must be absorbed to increase the repulsive forces between the chlorine nuclei until the atoms are forced apart.
- **D.** The process is exothermic (\(\Delta H^\circ < 0\)) because isolated chlorine atoms have a lower potential energy and greater thermodynamic stability than the bonded \(\text{Cl}_2\) molecule.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119775/*