energetics

• Hess’s Law

  enthalpy change for a reaction is independent of the route take
• formation

  formation of 1 mole of a substance from its elements in their standard states under standard conditions
• Hess’ cycle depends on

  data given, not what you are calculating
• due to Hess’s Law, how does the enthalpy change differ between the indirect route and the direct route in a reaction?

  It doesn’t, enthalpy change is the same
•  ∆Hf means

  enthalpy of formation
•  what is the ∆Hf of all elements


  0
• how do you find  ∆H in a reaction?

  sum of the  ∆fH of products - sum of the  ∆fH f reactants
•  ∆Hc

  enthalpy change for combustion of 1 mole of substance, where all the substances are in their standard states under standard conditions