Enthalpy change

• The enthalpy change (ΔH) is equal to the heat capacity multiplied by the temperature change, or Q = mcΔT.
• mean bond enthalpy:

  also known as bond energy, the amount of energy required to break 1 mole of the stated bond in the gaseous state, averaged over a range of compounds.
• Enthalpy change of combustion:

  The enthalpy change of 1 mole of a substance is completely burnt in oxygen under standard conditions, all reactants being in their standard states.
• Enthalpy change of formation:

  enthalpy change when 1 mole of a compound is from its elemenst at their standard states and under standard conditions.
• Hess's law:

  the enthalpy change of a chemical reaction is the same, no matter what route is taken from reactants to products.