bond enthalpy
- Created by: Jasmin
- Created on: 22-01-14 09:11
View mindmap
- Bond Enthalpy
- Bond enthalpy is the energy
- Required to break 1 mole of bonds
- Released on making 1 mol of bonds
- Energy to break bonds so bond breaking is endothermic (+)
- Energy is released when bonds are formed, so is exothermic (-)
- Amount of energy you need per mol is called bond dissociation enthalpy or bond enthalpy
- Bond enthalpies influence how quickly a reaction will occur. In general the smaller the bond enthalpies of the bonds that need to be broken, the faster a reaction will be at room temp. That's because less energy has to be taken in from the surroundings to break the reactant bonds
- Ethanol is used as a fuel. The enthalpy of combustion can be determined experimentally and also theoretically from mean bond enthalpy data.
- Example
- For mean bond enthalpy take an average
- Breaking bonds is always an endothermic process so average bond dissociation enthalpies are always positive
- Difference between calculated and experimental values arises because:
- Calculations use average (mean) bond enthalpies
- Bond enthalpies only apply to substances in the gaseous state
- As in the example, it is a liquid the energy of vapourisation must be added
- Bond enthalpy is the energy
Comments
No comments have yet been made