chap 9 chemical energetics

• how is thermal energy transferred during endothermic reactions ?

  thermal energy is absorbed, causing a decrease in temperature of the surroundings
• how is thermal energy transferred during exothermic reactions ?

  thermal energy is released to the surroundings, causing an increase in temperature of the surroundings
• is thermal decomposition endo or exo ?

  endo
• is electrolysis of water endo or exo ?

  endo
• is photosynthesis endo or exo ?

  endo
• is boiling and melting endo or exo ?

  endo
• is sublimation endo or exo ?

  endo
• is dissolution of ionic compounds in water endo or exo ?

  endo
• is neutralisation endo or exo ?

  exo
• is combustion endo or exo ?

  exo
• is respiration endo or exo ?

  exo
• is freezing and condensation endo or exo ?

  exo
• is dissolution of acids and alkalis in water endo or exo ?

  exo
• what is bond energy ?

  it is the amount of energy absorbed to break one mole of a chemical bond and is also the amount of energy released when one mole of that bond is formed
• what is activation energy ?

  it is the minimum amount of energy that colliding reactant particles must possess to react with each other
• what enthalpy change does endothermic reactions have ?

  positive
• what enthalpy change does exothermic reactions have ?

  negative
• what happens during endothermic reactions ?

  • the energy absorbed for bond breaking is greater than the energy released during bond forming
  • the products contain more energy than the reactants
  • temperature of the surroundings decreases
• what diagram is this ?

  energy level diagram

  
• what diagram is this ?

  energy profile diagram

  
• what happens during exothermic reactions ?

  
  

  • the energy released for bond forming is greater than the energy absorbed during bond breaking
  • the reactants contain more energy than the products
  • temperature of the surroundings increases
• how to calculate overall enthalpy change ?

  total energy absorbed - total energy released