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Calculate the resonance energy in CH_(3)COOH from the following data if the observed heat of formation of CH_(3)COOH is -439.7 kJ. {:("Bond energy (kJ)",,"Heat of atomisation (kJ)"),(C-H=413,,C=716.7),(C-C=348,,H=218.0),(C=O=732,,O=249.1),(C-O=351,,),(O-H=463,,):} |
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Answer» Solution :Calculation of `DeltaH_(f)(CH_(3)COOH)`: `2C(s)+2H_(2)(g)+O_(2)(g) to CH_(3)COOH[H-underset(H)underset(|)overset(H)overset(|)(C)-overset(O)overset(||)(C)-O-H]` For reactants : Heat of atomisation of 2 moles of `C=2xx716.7=1433.4 KJ` Heat of atomisation of 4 moles of `H=4xx218.0=872.0 kJ` Heat of atomisation of 2 moles of `O=2xx249.1=498.2 kJ` For products : Heat of FORMATION of 3 moles of`C-H=-(3xx413)=-1239 kJ` Heat of formation of 1 moles of `C-C=-(1xx348)=-348 kJ` Heat of formation of 1 moles of `C-O=-(1xx732)=-732 kJ` Heat of formation of 1 moles of `C-O=-(1xx351)=-351 kJ` Heat of formation of 1 mole of `O-H=-(1xx463)=-463 kJ` Resonance energy in `CH_(3)COOH=xkJ ("say")` Adding algebraically, we get `DeltaH_(f)` of `CH_(3)COOH` `-329.4+x=-439.7 ("given")` `:. x=-110.3 "kJ mole"^(-1)`. |
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