AP Chemistry / Unit 6: Thermochemistry
6.7 Bond Enthalpies
Notes
$$\Delta H=\sum(\text{bonds broken})-\sum(\text{bonds formed})$$
- Breaking bonds costs energy; forming bonds releases energy.
Practice
Bonds broken: 1,000 kJ. Bonds formed: 1,300 kJ. $\Delta H=$
$1000-1300$.
A reaction is exothermic when the bonds formed are:
More energy released than used.
Bond enthalpies give $\Delta H$ values that are:
Bond energies vary by molecule.
Ready for more? Take the Unit 6 test.