The enthalpy of atomisation of CH4 and C2H6 are 360 and 620 k cal mol−1 respectively. The C - C bond energy is expected to be ?
80 k cal mol−1
CH4(aq)→C(g)+4H′(g)ΔH=360 k cal
Hence, C - H bond energy =3604=90k cal mol−1
Hence, HC−C+6HC−H=620
Or HC−C=620−6HC−H=620−6×90=80 k cal