# Calculate the bond energy of $Cl-Cl$ bond from the following data:  $CH_4(g) + Cl_2(g) \rightarrow CH_3Cl(g) + HCl(g); \Delta H = -100.3\: kJ$. Also the bond energies of $C-H,\: C-Cl,\: H-Cl$ bonds are 413, 326 and 431 kJ/mol respectively.

$\begin {array} {1 1} (A)\;-243.7\: kJ/mol & \quad (B)\;243.7\: kJ/mol \\ (C)\;444.3\: kJ/mol & \quad (D)\;-444.3\: kJ/mol \end {array}$

$\Delta H$ = [Total energy required] – [Total energy released]
$\Rightarrow -100.3 = [ \Delta H_{C-H} + \Delta H_{Cl-Cl} ] – [ \Delta H_{C-Cl} + \Delta H_{HCl} ] = 413 + x -326 -431$
$\Rightarrow x = 344 – 100.3 = 243.7 \: kJ/mol$
Ans : (B)