enthalpy Flashcards
define enthalpy change
amount of heat released or absorbed by a chemical reaction carried at a constant pressure
define exothermic
heat energy released to surroundings
deltaH= negative
define endothermic
heat energy is absorbed from surroundings
delta h = positive
define average bond enthalpy
breaking of 1 mole of bonds in gaseous molecules by homolytic fission
what are the standard conditions?
25 degrees celcius
100KPa
solutions conc 1 moldm-3
define standard enthalpy of reaction
enthalpy change that accompanies a reaction in molar quantities expressed in a chemical equation under standard conditions - all reactants and products in their standard states
define standard enthalpy of neutrilisation
enthalpy change that accompanies the formation of one mole of H2O from neutralisation under standard conditions
define enthalpy change of formation
enthalpy change when one mole of a compound is formed from its elements in their standard states under standard conditions
define standard enthalpy change of combustion
enthalpy change for complete combustion of one mole of a substance under standard conditions and reactants and products in their standard states
define hess’s law
enthalpy change of a reaction depends only on initial and final states and is independent of the route taken
how can one determine if an enthalpy change has occurred?
temperature change
total heat energy equation
Q=mc deltaT
enthalpy change equation
Q/moles
suggest why your calculated enthalpy change from practical may be diff to standard enthalpy change of solution
1.heat loss or gained so deltaT is smaller than should be
2.conditions in practical not standard
formula for enthalpy change of a reaction
enthalpy of products - enthalpy of reactants
