Enthalpy & First Law
Easychemistry
For the reaction: 2C(graphite) + O2(g) → 2CO(g), ΔH = -221 kJ. What is the enthalpy change (ΔH) per mole of CO formed?
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Solution
Incorrect! Answer:
-110.5 kJ mol⁻¹
- Stoichiometry: The balanced equation shows that 2 moles of CO(g) are produced.
- Enthalpy Interpretation: The given ΔH=−221 kJ is the heat released when the reaction occurs exactly as written (i.e., for 2 moles of CO).
- Molar Enthalpy: To find the enthalpy change per mole, we divide the total enthalpy by the number of moles of the product of interest.
- Calculation: ΔHper mole=2 moles−221 kJ=−110.5 kJ/mol.
- Signify: The negative sign indicates an exothermic process.
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About This Question
- Subject
- chemistry
- Chapter
- chemical thermodynamics
- Topic
- enthalpy & first law
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
-110.5 kJ mol⁻¹
- Stoichiometry: The balanced equation shows that 2 moles of CO(g) are produced.
- Enthalpy Interpretation: The given ΔH=−221 kJ is the heat released when the reaction occurs exactly as written (i.e., for 2 moles of CO).
- Molar Enthalpy: To find the enthalpy change per mole, we divide the total enthalpy by the number of moles of the product of interest.
- Calculation: ΔHper mole=2 moles−221 kJ=−110.5 kJ/mol.
- Signify: The negative sign indicates an exothermic process.
This easy difficulty chemistry question is from the chapter chemical thermodynamics, covering the topic of enthalpy & first law. It appeared in the 2025 exam.
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