Calculate the enthalpy of the following reaction: H2C=CH2(g)+H2(g)→CH3−CH3(g) The bond energies of C−H,C−C,C=C and H−H are 99,83,147 and 104kcal respectively.
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Solution
The reaction is given as (figure) ΔH= Sum of bond energies of reactants − Sum of bond energies of products [ΔHC=C+4×ΔHC−H+ΔHH−H]−[ΔHC−C+6×ΔHC−H] =(147+4×99+104)−(83+6×99) =−30kcal