Enthalpy of formation of A2B is +1000 KJ. Ratio of bond enthalpies of A2,B2 and A2B is 1 : 2 : 1. Bond enthalpy of B2would be
Ratio of bond enthalpies of A2:B2:A2B is 1 : 2 : 1
B.E of A2=x
B.E of B2=2x
B.E of 12B2=x
B.E of A2B=x
∴A2x+12B2x→ A2Bx;ΔH=+1000kJ
ΔHB.D.E=HR−HP
+1000kJ =2x -x
x=1000kJ
B.D.E of B2 = 2x =+2000kJ