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ChemistryJEE Main 24 Jan 2026, Shift 2·Q17·MCQ·Moderate

Thermodynamics · Bond enthalpy from atomisation

The heats of atomisation of methane and ethane are ‘x' kJ mol−1^{-1} and ‘y' kJ mol−1^{-1} respectively. The longest wavelength (λ\lambda) of light capable of breaking the C-C bond can be expressed in SI unit as :
  1. (1)hc1000(y−6x4)−1\dfrac{hc}{1000}\left(\dfrac{y-6x}{4}\right)^{-1}
  2. (2)NAhc250(4y−6x)\dfrac{N_\mathrm{A}hc}{250(4y-6x)}
  3. (3)NAhc250(y−6x)\dfrac{N_\mathrm{A}hc}{250(y-6x)}
  4. (4)NAhc(y−6x4)−1N_\mathrm{A}hc\left(y-\dfrac{6x}{4}\right)^{-1}
We corrected a printing error in the original paper

Source printed “The heat of atomisation of methane and ethane are”.

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