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ChemistryJEE Main 21 Jan 2026, Shift 2·Q6·MCQ·Easy–moderate

Thermodynamics · Bond enthalpy from formation enthalpy

Consider the following data:

ΔfH⊖\Delta_\mathrm{f}H^\ominus(methane, g) =−X= -X kJ mol−1^{-1}

Enthalpy of sublimation of graphite =Y= Y kJ mol−1^{-1}

Dissociation enthalpy of HX2\ce{H2} =Z= Z kJ mol−1^{-1}

The bond enthalpy of C – H bond is given by:

  1. (1)X+Y+2Z4\dfrac{X+Y+2Z}{4}
  2. (2)X+Y+4Z2\dfrac{X+Y+4Z}{2}
  3. (3)X+Y+ZX+Y+Z
  4. (4)−X+Y+Z4\dfrac{-X+Y+Z}{4}

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See the full 21 Jan 2026, Shift 2 paper