Practice Energetics/thermochemistry (4) - Chapter 4: Energetics/Thermochemistry

Practice: Energetics/Thermochemistry

Lesson 4Energetics/Thermochemistry

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10 questions

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6 sample questions

Question 1.
What is the definition of enthalpy?
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Think about what heat content represents in thermodynamics.
Question 2.
What does a negative ΔH indicate?
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Remember 'E for Exit' related to heat leaving the system.
3Question 3.
What is the enthalpy change for an exothermic reaction?
- Positive
- Negative
- Zero
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Think about the direction of heat flow.
4Question 4.
Hess's Law states that the total enthalpy change is the same regardless of the pathway taken. (True/False)
- True
- False
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Consider how you can break down reactions into steps.
Question 5.
Using standard enthalpies of formation, calculate the enthalpy change for the reaction of carbon, hydrogen, and oxygen forming glucose: C(s) + H₂(g) + O₂(g) → C₆H₁₂O₆(s). Given values: ΔH_f°(C) = 0, ΔH_f°(H₂) = 0, ΔH_f°(O₂) = 0, ΔH_f°(C₆H₁₂O₆) = -1273 kJ/mol.
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Sum the formation enthalpies of products and subtract the reactants.
Question 6.
Estimate the ΔH for the reaction: C₂H₄(g) + H₂(g) → C₂H₆(g) using bond enthalpies. Given values: C=C = 611 kJ/mol, C-H = 412 kJ/mol.
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List all bonds involved and their bond enthalpy values.

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