minimum energy required to start a reaction by the breaking of bonds
Bond enthalpy?
heat energy required heat energy to break one mole of a given covalent in the molecules in the gaseous state
Mean bond enthalpy?
same covalent bond may appear in different compounds
Limitations of bond energy calculations
Uses mean values rather than specific ones
Not all substances are gases
Not all substances are covalent
Standard Enthalpy of formation?
the enthalpy change that occurs when one mole of a compound is formed from its constituent elements with all reactants and products in their standard states
Bu definition standard enthalpy formation of an element in its standard state is zero
Standard Enthalpy of combustion?
The enthalpy change that occurs when one mole of a compound reacts completely in oxygen with all reactants and products in their standard states
q = m c theta
q = m c delta T
Why is the experimental value less than the data book?
Lost some of heat to surroundings
incomplete combustion can occur
some evaporated as fuel is highly volatile
none standard conditions
Standard State?
Physical state of a substance under standard conditions
