Chemical bonds are broken to supply us with energy. Without bonds, and our ability to break them, the food we eat would not supply us with energy.
<span> 1C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O, the ∆H is –2200 kJ
1mol </span>C3H8(g) ---- –2200 kJ
2mol C3H8(g) ----2(–2200 kJ)=-4400kJ
