Thermochemistry

• Activation energy

  The minimum amount of energy required for a reaction to occur, starts with bond breaking
• Average bond enthalpy

  The amount of energy required to break one mole of bonds of a particular type between 2 atoms in a gaseous state
• Bond enthalpy

  The energy required to break a particular covalent bond in one mole of a molecule in a gaseous state
• Conservation of Energy

  Energy can neither be created or destroyed, only converted from one form of energy to another
• Endothermic reaction

  Any chemical reaction that absorbs heat from its environment
• Enthalpy

  The amount of energy released or absorbed when one mole of a substance is formed or consumed during a chemical reaction under standard conditions.
• Enthalpy change

  The amount of heat energy transferred during a chemical reaction at constant pressure
• Exothermic reaction

  A chemical reaction that releases energy by light or heat
• Hess's law

  The energy change in an overall chemical reaction is equal to the sum of energy change in the individual reactions comprising it
• Specific heat capacity

  The amount of heat it takes to change the temperature of one gram of a substance by 1 degree
• Standard conditions

  • All substances are in their standard state
  • 298K (25 degrees)
  • A pressure of 1 bar (101kPa)
• Standard enthalpy - Change of combustion

  The enthalpy change which occurs when one mole of the compound is burned completely in oxygen under standard conditions and with everything in its standard state
• Standard Enthalpy - Change of Formation

  The enthalpy change which occurs when one mole of a compound is formed from its element under standard conditions and with everything in its standard state
• Enthalpy change = Bonds broken - Bonds Formed