CHEM101 Lecture Notes - Lecture 16: Bond-Dissociation Energy, Triple Bond, Enthalpy
25 May 2018
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CHEM101 – Lecture 16 – Chemical Bonding
Enthalpy
• Bond enthalpy- measures the stability of a molecule
o Change associated with breaking a particular bond in 1 mole
▪ Gaseous molecule
o Tells us strength and stability of the molecule
• Table 8.6: Bond enthalpies
o
▪ Single bond- 347
• Weaker bond
▪ Double bond- 620
▪ Triple bond- 812
• Stronger because it has a higher value for bond enthalpy
o As bonds get larger we need more energy to break that bond
o If something is really strong, it is more stable
o Multiple bonds are shorter and stronger
•
o Total energy input (to break bonds) – total energy released (bonds formed)
o Estimate for the following reaction:
o ***there are 2 dots above the 2 N’s on the left side of the arrow!!
▪
H H
• Broken:
• Formed:
• Negative value for bond enthalpy= exothermic, releasing head
