TOPIC 2.1 - ENERGETICS
Exothermic - Give out heat (NEGATIVE) - /\H is NEGATIVE
Endothermic - Take in heat (POSITIVE) - /\H is POSITIVE
/\H - Enthalpy Change - The Enthalpy change for a reaction is the heat energy change measured under conditions of constant pressure.
The Standard Enthalpy Change for a reaction is the heat energy change measured under standard conditions: 100kPa and 298K (and all reactants+products in their standard states).
Enthalpy changes are measured in kJmol -1
So /\H= heat energy change/no. moles (/\H= Q/mol)
STANDARD ENTHALPY OF FORMATION - The Enthalpy change, under standard conditions, when 1 mole of compound is formed from it's elements with all reactants and products in their standard states.
STANDARD ENTHALPY OF COMBUSTION - The Enthalpy change, under standard conditions, when 1 mole of substance is burnt in excess Oxygen, with all reactants and products in their standard states.
----- THE STANDARD ENTHALPY OF FORMATION OF ALL ELEMENTS IN THEIR STANDARD STATES IS 0 -----