AP Chemistry 2.2.A: Intramolecular Forces and Potential Energy

Explore AP Chemistry 2.2.A questions on potential-energy curves, equilibrium bond length, bond energy, bond order, ion size, and Coulombic interactions.

Exam points

Explain how solutions form from solute-solvent interactions and how concentration affects their properties.
Apply molarity, dilution and precipitation concepts to calculate solution composition from experimental data.

[Maximum number: 3]

In the gas phase, $\mathrm{AlCl}_{3}$ is a molecular substance. A reaction of gaseous $\mathrm{AlCl}_{3}$ at high temperature is represented by the following balanced equation.

\text { Reaction 1: } \mathrm{AlCl}_{3}(g) \rightarrow \mathrm{Al}(g)+3 \mathrm{Cl}(g) \quad \Delta H_{1}^{\circ}=\text { ? }

(a)

A potential energy diagram for $\mathrm{Cl}_{2}$ is shown in the following graph.

[ 3 ]

(i)

Based on the graph, what is the bond length, in picometers, for $\mathrm{Cl}_{2}$ ? -

[ 1 ]

(ii)

A student finds that the average Al-Cl bond length is 220 picometers and the average bond energy is $425 \mathrm{~kJ} / \mathrm{mol}$ . Draw the potential energy curve for the average Al-Cl bond on the preceding graph.

[ 2 ]

For a curve with a minimum at an internuclear distance of 220 ± 10 pm: 1 point
See sample curve below
For a curve with a minimum energy value of $-425 \pm 20 \mathrm{~kJ} / \mathrm{mol}$ that approaches zero as the 1 point internuclear distance approaches 500 pm:

Figure for Answer to Question (ii) — AP Chemistry

Total for part (c) 3 points

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2.2.A—Represent the relationship between potential energy and distance between atoms, based on factors that influence… question 1

Question (a)

Question (i)

Question (ii)