Zusammenfassung der Ressource
DF4
- Bond enthalpies
- Chemical bond
= electrical
attraction
between atoms
or ions
- Bond enthalpy = Qunatity of energy required
to break a particular bond in a molecule
- Bond enthalpy will
be a negative value
if exothermic
- Greater the bond enthalpy the stronger the bond
- Equilibrium bond length = Attractive and
opposing forces with in bond are equal
- Shorter bond length = stronger bond
- Double bond = high B.E
Triple bond = V.high B.E
- Average bond enthalpies
used; exact value is
dependent on particular
compound bond is found.
- Bond enthalpies measured
indirectly using enthalpy cycles
- Usefull links
- http://www.lisgar.net/magwood/sch4u%20bonding%203.htm
- http://www.chemguide.co.uk/physical/energetics/sums.html
- Breaking and making bonds
- CH4 + 2 O2 = CO2 + 2 H2O
- ΔH = -890 KJmolmol-1
- Is breaking bonds and
creating new ones
- Worked out by looking at structure of reactants and products
- Always refers to breaking a bond in a gaseous compound
- Combustion of methane = exothermic
- energy in bond-breaking steps < energy in bond-making
- Not all have to be broken to form new ones