AB,A2 and B2 are diatomic molecules.If the bond energy of A2,AB and B2 are in the ratio 1:1:0.5 and enthalpy of formation of AB from A2 and B2 is -100 kJ/mol.What is the bond enthalpy of A2?

let energy of formation of A2 be E,

then reaction is

1/2 A2 +1/2 B2 -> AB

energy of o.5 mol A2 bond = 0.5 E

energy of o.5 mol B2 bond = 0.5 E/2 (as ratio is 0.5)

energy of 1 mol AB = E (as ratio 1)

total energy = E- 0.75E=0.25E that is -100
so E=-400kj/mol


  • 53
400 ki/mol
  • -2
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