Enthalpy Changes 1

• State Hess's law

  Enthalpy change of a reaction is independent of the route taken as long as both products and reactants remain the same
• Define Enthalpy of Formation

  The enthalpy change when 1 mole of a substance is formed from its constituent elements under standard states and standard conditions

  A) Arrows point upwards

  
• Define Enthalpy of Combustion

  The Enthalpy change when 1 mole of a compound is burned completely in oxygen where all reactants and products are in their standard states and standard conditions

  A) arrows point downwards

  
• Define Enthalpy Change

  Heat/Energy change under a constant pressure
• What are the Standard conditions

  100 kPa pressure

  298K Temperature

  reactants and products in their standard states
• An exothermic reaction is one that

  releases heat to the surroundings

  
  

  Bond breaking

  
• Endothermic reaction is one that

  Takes in energy from its surroundings

  
  

  bond breaking

  
• Define Activation energy

  The minimum energy required for a reaction to take place
• Calorimetry practical 


  q = m* c * change in Temp

  Enthalpy change = Q/1000/ n (moles)

  
• Name and an error in calorimetry practical and how to fix it

  Not letting reaction go to completion

  Fix by stirring solution with a thermometer
• Name another 2 errors in the calorimeter practical

  Incomplete combustion

  heat loss, dissipated to the beaker