Hess law and cycle

• What is Hess's law?

  Enthalpy change depends only on initial and final states
• What direction do the arrows point if the question asks about formation

  Upwards (creating > God)
• What direction does the arrows point if the question asks about combustion

  downwards ( hell and fire )
• What is the equation if the question asks about formation

  Products - reactants (fat penguins roll )
• What’s the equation if combustion is asked about

  Reactants - products (CRaP)
• How do you determine what method to do

  look at the data, if it’s formation Hf or combustion Hc
• How do you determine if it’s combustion or formation data if Hf or Hc isn’t given

  If it’s combustion equation given, correspond the enthalpy data to the element which the oxygen reacts with , eg carbon or hydrogen

  
  

  if its formation equation given, correspond the enthalpy data given to the product in the equation
• If asked why two answers differ and one uses mean data

  one answer uses average bond enthalpy data which are average values taken from a range of different compounds