AP Chemistry Unit 6.8: Enthalpy of Formation
Practice AP Chemistry Unit 6.8 questions on calculating standard reaction enthalpy from tabulated formation enthalpies for products and reactants.
- Syllabus
- Effective Fall 2025
- Course
- AP Chemistry
Exam points
- Use molecular structure and bonding models to predict polarity, intermolecular forces, solubility, and behavior.
- Interpret structural and particle data to explain how geometry and bonding determine observable properties.
Covered syllabus points
6.8 Enthalpy of Formation question 1
A student places a mixture of plastic beads consisting of polypropylene (PP) and polyvinyl chloride (PVC) in a 1.0 L beaker containing distilled water. After stirring the contents of the beaker vigorously, the student observes that the beads of one type of plastic sink to the bottom of the beaker and the beads of the other type of plastic float on the water. The chemical structures of PP and PVC are represented by the diagrams below, which show segments of each polymer.
PP
Using the table of standard enthalpies of formation below, determine whether the combustion of 2.00 mol of propene releases more, less, or the same amount of energy that 2.00 mol of vinyl chloride releases. Justify your answer with a calculation. The balanced equation for the combustion of 2.00 mol of propene
is \(2 \mathrm{C}_{3} \mathrm{H}_{6}(g)+9 \mathrm{O}_{2}(g) \rightarrow 6 \mathrm{CO}_{2}(g)+6 \mathrm{H}_{2} \mathrm{O}(g)\).
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