AP Chemistry Unit 7.4: Equilibrium Constants

Practice AP Chemistry Unit 7.4 questions on calculating Kc or Kp from equilibrium concentrations or partial pressures using stoichiometric changes.

Exam points

Use particle, bonding, and equilibrium models to explain solubility, phase changes, and solution composition.
Interpret molecular structure and experimental data to predict physical properties and species behavior.

Covered syllabus points

7.4.A—Calculate Kc or Kp based on experimental observations of concentrations or pressures at equilibrium

[Maximum number: 1]

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 { ? }

Using the particle-level diagram, calculate the value of $K_{p}$ for the reaction if the total pressure in the container is 22.1 atm.

For the correct calculated value, consistent with part (e): 1 point

K_{p}=\frac{\chi_{\mathrm{Al}_{2} \mathrm{Cl}_{6}}\left(P_{\text {total }}\right)}{\left(\chi_{\mathrm{AlCl}_{3}}\left(P_{\text {total }}\right)\right)^{2}}=\frac{\frac{3}{10}(22.1)}{\left(\frac{7}{10}(22.1)\right)^{2}}=0.0277

Total for question 210 points

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Covered syllabus points

7.4 Calculating the Equilibrium Constant question 1