Practice Applications Of Hess's Law (4.2.2) - Chapter 4: Energetics/Thermochemistry

Practice: Applications of Hess's Law

Lesson 4.2.2Energetics/Thermochemistry

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6 sample questions

Question 1.
Define Hess's Law in your own words.
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Think about how energy changes with different processes.
Question 2.
What is ΔH_f°?
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Focus on the conditions and what’s being formed.
3Question 3.
What does Hess's Law state?
- Total enthalpy is path-independent
- Total enthalpy is path-dependent
- Only exothermic reactions follow Hess's Law
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Consider the meaning of state functions.
4Question 4.
True or False: The standard enthalpy of formation for an element is always zero.
- True
- False
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Think about the elements in their natural forms.
Question 5.
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.
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Is the reverse of a reaction equal to its original enthalpy change?
Question 6.
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.
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What does this imply about the state function of enthalpy?

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