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Enthalpy and Energy

  • An exothermic reaction is where energy is released from chemical bonds.
  • An endothermic is  where energy is taken in to form the chemical bonds.
  • Enthalpy is the heat energy content of a compound at constant pressure.
  • ΔH represents the Change in Enthalpy 
  • An exothermic reaction will have a negative Enthalpy Change, an endothermic will have a positive Enthalpy change.
  • The standard conditions for measuring Enthalpy Change are: 298K, 100kPa and the values are giver per mole.
  • ΔH = H products - H reactants
  • Calorimetry is the measuring of heat. 
  • A catalyst doesn't affect the ΔH of a reaction.
  • Heat energy required (Q) for a recation to occur is often calculated 
  • Q=MCΔT: M


Aishah Javed


Useful but can u tell me how to calculate the enthalpy 



Very useful for someone recapping AS for A2 level.

However endothermic is actually breaking bonds, and exothermic is actually making bonds.

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