Calorimetry

Calorimetry

method for measuring energy released by chemical reactions
Q=mcdeltaT
1. Q=energy in joules
2. m=mass of water in grams
3. c=specific heat capacity of water(4.2 J/g degrees celsius)
4. delta T=change in temp
errors
1. lot of heat loss to the surroundings
2. not all of the food/fuel burns
3. water should be stirred
4. some energy heat the container
Energy level diagrams
1. supply energy to break bonds
2. energy released when making bonds
3. exothermic - energy given out (high energy level to low level energy
  1. energy released from forming new bonds is greater than energy needed to break bonds
  2. eg combustion/neutralisation
  3. deltaH is negative
4. activation energy
  1. catalyst can provide a different pathway that has a lower activation energy
  2. the minimum amount of energy that colliding reactant particles must have for a reaction to occur
5. endothermic-energy taken in (low energy level to high energy level)
  1. energy needed to break bonds is greater than the energy released from forming new bonds
  2. deltaH is positive
  3. thermal decomposition
6. Bond energies
  1. the amount of energy needed to break a particular chemical bond
  2. measured in KJ/mole
  3. 1) calculate total amount of energy needed to break all the bonds in reactants
    1. 2) calculate total amount of energy released in making all the bonds in products
      1. 3) overall energy change = energy in - energy out
  4. exothermic reaction, the energy needed to break existing bonds is less than the energy released from forming new bonds
  5. endothermic reactions , the energy needed to break existing bonds is more than the energy released from forming new bonds

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