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The heat of formation of methane is -17.9 kcal. If the heats of atomisation of carbon and hydrogen are 170.9 and 52.1 kcal per mole, Calculate the C-H bond energy in methane. |
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Answer» Solution :GIVEN that `C(s)+2H_(2)(g) to CH_(4)(g)`, `DeltaH=-17.9kcal` Energy change in reactants Heat of atomisation of 1 mole of C `=170.9` KCAL Heat of atomisation of 4 moles of H `=4xx52.1` kcal Energy change in product Heat of formation of 4 moles of C-H bonds `=4xx x `kcal (where x is the energy of formation of C-H bonds in kcal/mole. ) Since the ALGEBRAIC sum of all the heat changes in equal to the heat of formation of the above given equation, we have `170.9+4xx52.1+4x=-17.9`, `x=-99.3` kcal Thus the bond energy `=+99.3` kcal/mole |
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