Question

If the bond energies of H–H, Br – Br and H –Br are 433, 192 and 364kJmol–1 respectively the ΔHo for the reaction H2(g)+Br2(g)→2HBr(g) is-

Answer 1

2 H-Br bonds are present so 2×364=728kjmol^-1. 1H-H bond so 433 and 1Br-Br bond so 192kjmol^-1. Products -reactants. 728-433-192=103kjmol^-1 is the  delta H value.