Practice Hess’s Law: Enthalpy Is Path-independent (2.2) - Unit 5: Energetics and Thermochemistry

Practice: Hess’s Law: Enthalpy Is Path-Independent

Lesson 2.2Unit 5: Energetics and Thermochemistry

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5 questions

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6 sample questions

Question 1.
Define Hess's Law.
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Think about how the overall energy change is concerned with initial and final states.
Question 2.
Explain the significance of Hess’s Law in thermochemistry.
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Consider how we can break down complex reactions into simpler parts.
3Question 3.
What does Hess's Law state?
- The overall energy change is affected by the pathway.
- Total enthalpy change is the same regardless of steps.
- Enthalpy cannot be measured directly.
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Focus on how the reaction can occur in different manners.
4Question 4.
True or False: Hess’s Law allows us to calculate unknown enthalpy changes.
- True
- False
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Consider how complex reactions can be approached.
Question 5.
Given the standard enthalpy of formation values for N₂(g)=0, O₂(g)=0, and ΔH_f°[NO(g)] = 90.3 kJ/mol, calculate ΔH for the reaction: N₂(g) + O₂(g) → 2NO(g).
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Remember that formation enthalpy values for elements in their standards states are zero.
Question 6.
Using Hess's Law, if the enthalpy change for the combustion of propane (C3H8) is -2043 kJ/mol, derive the enthalpy change for the formation of propane.
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Think about how reversing a reaction changes the sign of ΔH.

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