Practice Standard Enthalpy Of Formation (δh_f°) (4.1.4) - Chapter 4: Energetics/Thermochemistry

Practice: Standard Enthalpy of Formation (ΔH_f°)

Lesson 4.1.4Energetics/Thermochemistry

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6 sample questions

Question 1.
What is the standard enthalpy of formation for an element in its most stable form?
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Think of a stable compound like carbon in graphite form.
Question 2.
What does ΔH_f° represent?
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It’s a formation reaction.
3Question 3.
What is the standard enthalpy of formation for elements in their most stable form?
- 0 kJ mol⁻¹
- -393.5 kJ mol⁻¹
- 20 kJ mol⁻¹
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It’s a benchmark value.
4Question 4.
Are exothermic reactions characterized by a positive or negative ΔH?
- True (they are negative)
- False (they are positive)
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Think about heat flow!
Question 5.
The standard enthalpy of formation for H₂O(l) is -285.8 kJ/mol. Calculate the enthalpy for the reaction 2H₂(g) + O₂(g) → 2H₂O(l).
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Use stoichiometric coefficients for the formation.
Question 6.
Given that the ΔH_f° for C(graphite) is 0 kJ/mol and for O₂ is also 0 kJ/mol, if ΔH_f° for CO₂ is -393.5 kJ/mol, determine the enthalpy change for a reaction producing CO₂ from its elements.
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Recap what ΔH_f° stands for in terms of formation from elements.

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