Enthalpy change is the heat energy transferred in a reaction at constant pressure (KJ mol-1).
Standard pressure is 100 KPa.
Exothermic reactions give out energy so the enthalpy is negative.
Endothermic reaction absorb energy so the enthalpy is positive.
Reactions are all about making and breaking bonds.
You need energy to break bonds so bond breaking is endothermic. Stronger bonds need more energy to be broken.
Energy is released when bonds are formed so bond forming is exothermic. Stronger bonds release more energy when they are formed.
The enthalpy change is the overall effect of the making and breaking of the bonds.
Comments
No comments have yet been made