Zusammenfassung der Ressource
Calculating energy changes
- Exothermic reactions give out heat
- If the energy given out is more
than it needs to break the bonds
the reaction is exothermic.
- Endothermic reaction take in heat
- Energy change= Total energy
needed to break all bonds-total
energy given out when new bonds are
formed
- Example CH4 + 2O2----> CO2 + 2H20
- 4*C-H=(4*412)=1648kj
- 2*O=O =(2*496)=992kj
- Total energy in = 2640kj
- Bonds formed are C=O and O-H
- 2*C=O =(2*743)=1486kj
- 4* O-H =(4*463) =1852kj
- Total energy out=3338kj
- Total energy change= 2640-3338=-698kj
- Exothermic reaction