ENTHALPY Flashcards
STANDARD ENTHALPY CHANGE OF FORMATION
the enthalpy change when 1 mole of a compound is formed from its elements in their standard states under standard conditions
ENTHALPY CHANGE FORMULA
enthalpy change = (total energy to break bonds) - (total energy released forming bonds)
Q = MC(delta)T
heat energy change = mass of solution x 4.18 x temperature change
enthalpy = q/moles
STANDARD CONDITIONS FOR ENTHALPY
25 degrees
100 kPa
STANDARD ENTHALPY CHANGE OF COMBUSTION
enthalpy change when 1 mole of a substance is completely burned in oxygen to make CO2 and H2O under standard conditions
WHAT IS THE ENTHALPY CHANGE OF A REACTION
The heat change of a reaction at a constant pressure (under standard conditions)
STANDARD ENTHALPY CHANGE OF NEUTRALISATION
enthalpy change when an acid and an alkali form 1 mole of water under standard conditions
What is an endothermic reaction and an example
one that absorbs energy from the surroundings
Thermal decomposition of calcium carbonate
What is an exothermic reaction and an example
one that releases energy to the surroundings
combustion of ethane
What is bond dissociation enthalpy
the energy needed per mole to break attractive forces in a bond (ONLY OCCURS IN GASEOUS COMPOUNDS)
What is calorimetry used for
to work out enthalpy change of reactions
What’s Hess’ law
The total enthalpy change of a reaction is independent of the route taken
Hess’ cycle of formation layout
Reactants products
elements in standard states
Hess’ cycle of combustion layout
Reactants/elements products
combustion products
