AP Chemistry Unit 6 practice questions: Thermochemistry
8 original multiple-choice questions on AP Chem Unit 6, thermochemistry. Answer each one in your browser and read the explanation, then review the key ideas below.
Question 1 of 8
For an exothermic reaction, which statement is true?
Question 2 of 8
How much heat is needed to raise 100 g of water by 10 °C? (c = 4.18 J/g·°C)
Question 3 of 8
Which statement about chemical bonds is correct?
Question 4 of 8
A → B has ΔH = −100 kJ and B → C has ΔH = +40 kJ. What is ΔH for A → C?
Question 5 of 8
When a salt dissolves in water in a coffee-cup calorimeter, the water gets colder. What does this tell you?
Question 6 of 8
How is ΔH for a reaction estimated from average bond enthalpies?
Question 7 of 8
How much heat does 50.0 g of water release when it cools by 20.0 °C? (c = 4.18 J/g·°C)
Question 8 of 8
While ice melts at 0 °C, heat is added but the temperature stays the same. Where does the energy go?
Key ideas in Unit 6
- Exothermic reactions release heat (ΔH < 0); endothermic reactions absorb it (ΔH > 0).
- Calorimetry: q = mcΔT. Heat lost by one part of a system equals heat gained by another.
- Phase changes happen at constant temperature; the energy changes the intermolecular attractions.
- Find ΔH three ways: Hess's law, enthalpies of formation (products minus reactants) and bond enthalpies (broken minus formed).
- Breaking bonds always absorbs energy and forming bonds always releases it.
More AP Chem practice
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Unit 7: Equilibrium →
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