Question

Bond dissociation enthalpy of CH4 is 360kJ/mol and C2H6 is 620kJ/mol. then bond dissociation energy of C-C bond is how much?

Answer 1

4(C-H)=360
C-H=90
AND
C-C+6(C-H)=620
C-C+6※90=620
C-C+540=620
C-C=620-540
C-C=80

Answer 2

The dissociated energy of 1 C-C bond = 80 $k cal mol^{-1}$

Explanation:

We are given dissociated energy of CH4 = 360 $k cal mol^{-1}$

Since, $CH_4$ has 4 CH bonds.

Dissociated energy of 1 CH bond = 360 ÷ 4 = 90 $k cal mol^{-1}$

The dissociation energy of $C_2H_6$ = 620 $k cal mol^{-1}$

Where $C_2H_6$ has 1 C-C bond and 6 CH bonds.  

So, we can calculate the dissociated energy of 1 C-C bond by:

C-C bond + 6CH bond = 620

C-C bond + (6 × 90) = 620

C-C bond + 540 = 620

C-C bond = 620 - 540 = 80 $k cal mol^{-1}$