5.2 - Standard Enthalpy Changes
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Practice Questions
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What are standard conditions in thermochemistry?
💡 Hint: Think about the definitions we discussed.
What does ΔH_f° represent?
💡 Hint: Remember the definition we talked about!
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Interactive Quizzes
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What is the standard enthalpy of formation (ΔH_f°)?
💡 Hint: Think of what formation means in thermodynamics.
True or False: Standard enthalpy of combustion (ΔH_c°) is always positive.
💡 Hint: Consider what happens during the combustion of fuels.
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Challenge Problems
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Given the enthalpy changes:
ΔH_f°[C₆H₁₂O₆] = -2,803 kJ/mol (glucose), calculate the heat liberated when burning 1 mole of glucose completely in excess oxygen using combustion data.
💡 Hint: Think back to combustion reactions and their enthalpy definitions.
Utilize Hess's Law to find ΔH for the reaction:
C₂H₄ + 3 O₂ → 2 CO₂ + 2 H₂O, using:
ΔH_f°[C₂H₄(g)] = +52.3 kJ/mol, ΔH_f°[CO₂(g)] = -393.5 kJ/mol, ΔH_f°[H₂O(l)] = -285.8 kJ/mol.
💡 Hint: Reference the formation equation while collecting enthalpy values.
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