Bond Enthalpies Flashcards Preview

AS Chemistry > Bond Enthalpies > Flashcards

Flashcards in Bond Enthalpies Deck (6)
Loading flashcards...
1

Bond enthalpies

Energy required to break 1 mole of a specified type of bond in a gaseous molecule
Endothermic, +ve value

2

Limitations of bond enthalpies

Actual bond enthlapy depends on chemical environment of bond
Average bond enthalpy calculated from actual bond enthalpies, no 1 true value
Not all enthalpy changes occur under standard conditions

3

Calculating enthalpy change from average bond enthalpy

Total bond enthalpy of reactants-total bond enthalpy of products=enthalpy change

4

Hess’ law

If a reaction can take place by 2 routes and the starting and finishing conditions are the same, total enthalpy change is the same

5

Hess cycle for the enthalpy change for delta f H

Reactants =>Products
^. ^
Elements

6

Hess cycle for the enthalpy change of delta c H

Reactant => Products
Combustion products