bond enthalpy

# bond enthalpy - o H-O 463 kJ/mol o O2 495 kJ/mol • 2 C-C...

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bond enthalpy  - enthalpy change for breaking of a bond   strength of covalent bond determined by amount of energy needed to break it always positive value DHrxn = (bond enthalpies of bonds broken) - (bond enthalpies of bonds formed) derived for gaseous molecules, only averaged values Find the DH for 2C2H6 + 7O2>> 4CO2 + 6H2O   C2H6 CO2 H2O Given bond enthalpies: o C-H 413 kJ/mol o C-C 348 kJ/mol o C=O 799 kJ/mol
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Unformatted text preview: o H-O 463 kJ/mol o O2 495 kJ/mol • 2 C-C, 12 C-H, 7O2 bonds broken • 8 C=O, 12 H-O bonds created • [2(348) + 12(413) + 7(495)] - [8(799) + 12(463)] = -2831 kJ Find the DH for N2H4 >> N2 + 2H2 • N2H4 • N2 • Given bond enthalpies: o N-H 391 kJ/mol o H-H 436 kJ/mol o N= N 941 kJ/mol o N-N 163 • 1 N-N, 4 N-H bonds broken • 1 N= N, 2 H-H bonds created • [163 + 4(391)] - [941 + 2(436)] = -86 kJ...
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