calculate the enthalpy change for the reaction :-

H2(g) + Cl2(g) → 2HCL(g)

given that the bond energies H-H,Cl-Cl,and H-Cl bonds are 433, 244 and 431kj/ mol respectively.

Energy absorbed for dissociation of 1 mole of H-H bonds = 433 kJ/mol
Energy absorbed for dissociation of 1 mole of Cl-Cl bonds = 244 kJ/mol
Total energy absorbed = 677 kJ/mol
Energy released in the formation of 2 moles of H-Cl bond = 431 x 2
  = 862 kJ/mol
Energy released  is greater than Energy absorbed
Hence, net result is the release of energy.
Energy released = 862 – 677
   = 185 kJ/mol

For the given reaction, ∆rH = - 185 kJ/mol

  • 8
What are you looking for?