Qhov Tseem Ceeb Qhov txawv - Bond Zog vs Bond Enthalpy
Ob daim ntawv cog lus lub zog thiab daim ntawv cog lus enthalpy piav txog tib lub tswv yim tshuaj; tus nqi ntawm lub zog yuav tsum tau sib cais ib tug mole ntawm molecules rau hauv nws cov khoom atoms. Qhov no ntsuas lub zog ntawm ib daim ntawv cog lus tshuaj. Yog li ntawd nws tseem hu ua bond zog. Lub zog daim ntawv cog lus yog xam raws li tus nqi nruab nrab ntawm daim ntawv cog lus dissociation energies ntawm 298 K rau tshuaj hom tshuaj nyob rau hauv lub gaseous theem. Tsis muaj qhov sib txawv ntawm cov lus cog lus lub zog thiab daim ntawv cog lus enthalpy, tab sis daim ntawv cog lus lub zog yog txhais los ntawm "E" whereas bond enthalpy yog denoted los ntawm "H".
Bond Energy yog dab tsi?
Bond zog lossis daim ntawv cog lus enthalpy yog qhov ntsuas ntawm daim ntawv cog lus lub zog. Bond zog yog lub zog uas yuav tsum tau ua kom sib cais ib qho mole ntawm molecules rau hauv nws cov atoms. Qhov no txhais tau hais tias lub zog ntawm daim ntawv cog lus yog lub zog xav tau los rhuav tshem cov tshuaj lom neeg. Bond zog yog denoted li "E". Chav ntsuas ntsuas yog kJ/mol.
Cov tshuaj tiv thaiv kab mob yog tsim los ntawm cov atoms txhawm rau kom tau txais lub xeev ruaj khov thaum tus neeg atoms muaj lub zog siab uas tsis ruaj khov. Qhov no txhais tau hais tias cov tshuaj tiv thaiv kab mob txo qis lub zog ntawm lub cev. Yog li ntawd, qee qhov ntawm lub zog raug tso tawm (feem ntau yog cov cua sov) thaum tsim cov khoom siv tshuaj. Yog li ntawd, kev tsim daim ntawv cog lus yog ib qho tshuaj tiv thaiv exothermic. Txhawm rau rhuav tshem cov tshuaj lom neeg no, lub zog yuav tsum tau muab (ib qho sib npaug ntawm lub zog rau lub zog tso tawm thaum daim ntawv cog lus). Tus nqi ntawm lub zog no yog hu ua daim ntawv cog lus lub zog lossis daim ntawv cog lus enthalpy.
Daim duab 1: Lub zog daim duab rau kev tsim daim ntawv cog lus (sab laug) thiab daim ntawv cog lus tsis sib xws (txoj cai).
Lub zog sib npaug sib npaug ntawm qhov sib txawv ntawm enthalpy ntawm cov khoom (atoms) thiab reactants (pib molecule). Txhua molecule yuav tsum muaj nws tus kheej daim ntawv cog lus zog qhov tseem ceeb. Tab sis muaj kev zam. Piv txwv li, daim ntawv cog lus lub zog ntawm C-H daim ntawv cog lus nyob ntawm lub molecule qhov twg cov nyiaj tau los. Yog li ntawd, lub zog daim ntawv cog lus yog xam raws li tus nqi nruab nrab ntawm daim ntawv cog lus dissociation energies.
Lub zog daim ntawv cog lus yog qhov nruab nrab daim ntawv cog lus sib koom ua ke rau tib hom nyob rau theem gaseous (ntawm 298 K kub). Piv txwv li, lub zog ntawm methane molecule (CH 4) yog lub zog xav tau los tsim cov pa roj carbon atom thiab 4 hydrogen radicals. Tom qab ntawd lub zog ntawm daim ntawv cog lus ntawm C-H daim ntawv cog lus tuaj yeem suav tau los ntawm kev siv cov txiaj ntsig ntawm kev sib koom ua ke ntawm txhua C-H daim ntawv cog lus thiab faib tag nrho tus nqi los ntawm 4.
Ex: Bond zog ntawm O-H daim ntawv cog lus hauv H2O molecule tuaj yeem xam raws li hauv qab no.
Ntau lub zog xav tau los rhuav tshem H-OH daim ntawv cog lus=498.7 kJ / mol
Tus nqi ntawm lub zog yuav tsum tau tawg O-H daim ntawv cog lus (hauv seem OH radical)=428 kJ / mol
Qhov nruab nrab daim ntawv cog lus sib faib zog=(498.7 + 428) / 2
=463.35 kJ/mol ≈ 464 kJ/mol
Vim li no, lub zog ntawm O-H hauv H2O molecule raug suav tias yog 464 kJ / mol.
Bond Enthalpy yog dab tsi?
Bond enthalpy lossis lub zog cog lus yog lub zog xav tau los cais cov molecule rau hauv nws cov atomic Cheebtsam. Nws yog ib qho kev ntsuas ntawm lub zog ntawm daim ntawv cog lus. Daim ntawv cog lus enthalpy yog txhais ua "H".
Qhov txawv ntawm Bond Zog thiab Bond Enthalpy yog dab tsi?
- Bond zog los yog daim ntawv cog lus enthalpy yog tus nqi ntawm lub zog yuav tsum tau tawg ib qho mole ntawm molecules rau hauv nws cov khoom atoms.
- Bond zog txhais tau tias "E" thaum daim ntawv cog lus enthalpy txhais tau tias "H".
Summary – Bond Energy vs Bond Enthalpy
Cov nyiaj cog lus lub zog lossis daim ntawv cog lus enthalpy yog lub zog xav tau los cais cov mole ntawm cov molecules rau hauv nws cov atomic Cheebtsam hauv theem gaseous. Nws yog xam los ntawm kev siv daim ntawv cog lus dissociation zog qhov tseem ceeb ntawm cov tshuaj bonds. Yog li ntawd lub zog daim ntawv cog lus yog qhov nruab nrab tus nqi ntawm daim ntawv cog lus dissociation energies. Nws yog ib txwm muaj txiaj ntsig zoo vim tias daim ntawv cog lus dissociation yog endothermic (bond formation is exothermic). Tsis muaj qhov sib txawv loj ntawm daim ntawv cog lus lub zog thiab daim ntawv cog lus enthalpy.
