The H−H bond energy is 430 kJ mol−1 and Cl−Cl bond energy is 240 kJ mol−1. ΔHf of HCl is −90 kJ. The H−Cl bond energy is (420+x) kJ mol−1, where x is:
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Solution
12H2(g)+12Cl2(g)→HCl ΔHF=−90KJ ΔHf= B.E for reactants - B.E for products. −90=4302+2402− B.E of HCl −90=215+120− B.E of HCl −90=335− B.E of HCl B.E. of HCl=335+90=425KJ−mole−1 ∴X=5.