Answer
$239$ kJ/mol
Work Step by Step
To solve this problem, we need to use the given information to calculate the bond energy of A2.
$\Delta E=E_{broken}-E_{formed}$
$\Delta E=D_{A_2}+D_{B_2}-2D_{AB}$
We know:
$\Delta E=-285$
$D_{B_2}=432$
$D_{A_2}=\frac{1}{2}D_{AB}\Rightarrow D_{AB}=2D_{A_2}$
We determine $D_{A_2}$:
$-285=D_{A_2}+432-4D_{A_2}$
$3D_{A_2}=717$
$D_{A_2}=\frac{717}{3}=239$
So the bond energy of $A_2$ is $239$ kJ/mol.
