The heat of atomization of methane and ethane are 360 kJ mol - 1 and 620 kJ mol - 1 , respectively. The longest wavelength of light capable of breaking the C - C bond is (Avogadro's number = 6.023 × 10 23 , h = 6.62 × 10 - 34 J s )

Step-by-step solution

4   B . E   ( C - H ) bond = 360   kJ   mol - 1 . B . E   ( C - H ) bond = 90   kJ   mol - 1 . In C 2 H 6 ,   B . E C - C + 6 × B . E C - H = 620   k J , B . E C - C bond = 620 - 6 × 90 = 80   kJ   mol - 1 , B . E C - C bond = 80 96 .48 = 0 .83   eV   bond - 1 . λ ( P h o t o n   i n   Å ) for rupture of E = hc λ The wave length required to break C - C bond = 12408 0 .83 = 14950 Å , = 1495   n m , ≈