Enthalpy
The enthalpy of combustion of methane at 298 K is −890 kJ mol⁻¹. What is the amount of heat released when 5.0 g of methane is completely burnt at this temperature?
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Solution
−278 kJ
- Find Moles of Methane:
- Molecular formula: CH4
- Molar mass =12(C)+4×1(H)=16 g/mol
- Moles of CH4=Molar massMass=165.0=0.3125 moles
- Calculate Heat Released:
- ΔHc=−890 kJ/mol (Heat released for 1 mole)
- Heat released =n×ΔHc=0.3125 mol×(−890 kJ/mol)=−278.125 kJ≈−278 kJ
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About This Question
- Subject
- chemistry
- Chapter
- chemical thermodynamics
- Topic
- enthalpy
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
−278 kJ
- Find Moles of Methane:
- Molecular formula: CH4
- Molar mass =12(C)+4×1(H)=16 g/mol
- Moles of CH4=Molar massMass=165.0=0.3125 moles
- Calculate Heat Released:
- ΔHc=−890 kJ/mol (Heat released for 1 mole)
- Heat released =n×ΔHc=0.3125 mol×(−890 kJ/mol)=−278.125 kJ≈−278 kJ
This medium difficulty chemistry question is from the chapter chemical thermodynamics, covering the topic of enthalpy. It appeared in the 2025 exam.
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