Question

Bond dissociation energy of $C{H}_4\text{is}360kJmo{l}^{-1}$ and $C_2{H}_6\text{is}620kJmo{l}^{-1}$. Then bond dissociation energy of $C-C$ bond is

• A. 170 kJ/mol
• B. 50 kJ /mol
• C. 80 kJ/mol
• D. 220 kJ/mol

Answer 1

The correct option is C 80 kJ/mol

$\text{Dissociation energy of methane}=360kJmo{l}^{-1}$

$\therefore$
$\text{Bond energy of C - H bond}=\frac{360}{4}=90kJ/mol$

$\text{Bond energy of ethane,}1B.E(C-C)+6B.E.(C-H)=620kJ/mol$
$B.E(C-C)+6\times 90=620B.E(C-C)+540=620B.E(C-C)=620-540B.E(C-C)=80kJmo{l}^{-1}$
$\text{Bond dissociation of C - C bond}=80kJmo{l}^{-1}$

Hence, option (c) is correct.