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#bond enthalpies

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Using bond enthalpies (C-H = 413 kJ/mol, O=O = 498 kJ/mol, C=O = 803 kJ/mol, O-H = 467 kJ/mol), calculate Δ H for CH₄(g)

Bonds broken: 4(C-H) + 2(O=O) = 4 × 413 + 2 × 498 = 1652 + 996 = 2648 kJ. Bonds formed: 2(C=O) + 4(O-H) = 2 × 803 + 4 × 467 = 1606 + 1868 = 3474 kJ. Δ H = 2648 - 3474 = -826 kJ/mol.

Ref: NCERT Class 11 Chemistry > Chapter 5: Thermodynamics > Topic: First Law of Thermodynamics and Enthalpy and Internal Energy