4.2.2 - Applications of Hess's Law
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Practice Questions
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Define Hess's Law in your own words.
💡 Hint: Think about how energy changes with different processes.
What is ΔH_f°?
💡 Hint: Focus on the conditions and what’s being formed.
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Interactive Quizzes
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What does Hess's Law state?
💡 Hint: Consider the meaning of state functions.
True or False: The standard enthalpy of formation for an element is always zero.
💡 Hint: Think about the elements in their natural forms.
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Challenge Problems
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Given the reactions: 2H₂ + O₂ → 2H₂O (ΔH = -572 kJ) and 2H₂O → 2H₂ + O₂ (ΔH = +572 kJ), confirm Hess's Law by deriving ΔH for the complete cycle.
💡 Hint: Is the reverse of a reaction equal to its original enthalpy change?
Calculate the ΔH for the following reaction using the provided reactions: N₂ + 3H₂ → 2NH₃. Given: ΔH (N₂ + 3H₂ → 2NH₃) = -92.4 kJ and ΔH (2NH₃ → N₂ + 3H₂) = +92.4 kJ.
💡 Hint: What does this imply about the state function of enthalpy?
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