The heat of atomization of methane and ethane are 360 kJ/mol and 620 KJ/mol, respectively. The longest wavelength of light capable of breaking the C-C bond is: (Avogadro number = 6.02 x 1023, h = 6.62 x 10-34 J s) 2.48 × 104 nm, 1.49 × 104 nm, 1.49 × 103 nm, 2.48 × 103 nm

The heat of atomization of methane is 360 kJ/mol. This corresponds to breaking of four C-H bonds. Hence, the heat corresponding to breaking of one C-H bond is 360/4 = 90 kJ/mol. The heat of atomization of ethane is 620 kJ/mol. This corresponds to breaking of one C-C bond and six C-H bonds. The heat corresponding to breaking of one C-C bond will be 620 - (6 × 90) = 80 kJ/mol. This corresponds to 1 mole. For one single bond, the required energy that can be obtained by dividing with Avogadro's number is given by; E = (80 × 1000) / (6.02 × 1023). The energy is related to wavelength by relation E = hc/λ. Substitute values in the above expression. (80 × 1000) / (6.02 × 1023) = (6.62 × 10-34 × 3 × 108) / λ. Hence, λ = 1.49 × 10-6 m = 1.49 × 103 nm.