THERMODYNAMICS/ENERGETICS Flashcards
WHAT DOES HESS’S LAW STATE
ENTHALPY CHANGE FOR A CHEMICAL REACTION IS INDEPENDENT OF THE ROUTE TAKEN
STANDARD ENTHALPY OF FORMATION
ENTHALPY CHANGE WHEN ONE MOLE OF COMPOUND FORMED FROM IT ELEMENTS UNDER STANDARD STATES (PRODUCTS + REACTANTS)
STANDRAD ENTHAPLY OF COMBUSTION
ENTHAPLY CHANGE WHEN ONE MOLE OF A SUBSTANCE IS COMPLETELY BURNT IN EXCESS O2
STANDARD ENTHALPY OF ATOMISATION
The enthalpy change when one mole of gaseous atoms are formed from an element in its standard state.
1ST IONISATION ENERGY
ENTHALPY CHANGE WHEN ONE MOLE OF e- IS REMOVED FROM ONE MOLE OF GASEOUS ATOMS TO FORM ONE MOLE OF GASEOUS 1+ IONS
2ND IONISATION ENERGY
ENTHALPY CHANGE WHEN ONE MOLE OF e- IS REMOVED FROM ONE MOLE OF GASEOUS +1 IONS TO FORM ONE MOLE OF GASEOUS 2+ IONS
1ST ELECTRON AFFINITY
ENTHAPLY CHANGE WHEN ONE MOLE OF GASEOUS ATOMS GAINS ONE MOLE OF e- TO FORM ONE MOLE OF GASEOUS 1- IONS
2ND ELECTRON AFFIONITY
ENTHAPLY CHANGE WHENONE MOLE OF GASEOUS 1- IONS GAINS ONE MOLE OF e- TO FORM ONE MOLE OF GASEOUS 2- IONS
LATTICE ENTHALPY OF FORMATION
ENTHALPY CHANGE WHEN ONE MOLE OF A SOLID IONIC COMPUND IS FORMED FROM ITS GASEOUS IONS
LATTICE ENTHALPY OF DISSOCIATION
STAMDARD ENTHALPY CHANGE WHEN ONE MOLE OF SOLID IONIC COMPOUND DISSCOCIATES INTO IOTS GASEOUS IONS
ENTHALPY OF SOLUTION
STANDARD ENTHALPY CHANGE WHEN ONE MOLE OF SOLUTE DISSOLVES TO FORM ITS AQUEOUS IONS
ENTHALPY OF HYDRATION
STANDARD ENTHALPY CHANGE WHEN ONE OF GASEOUS IONS IS CONVERTED INTO ONE MOLE OF AQEUOUS IONS
MEAN BOND DISSOCIATION ENTHALPY
Mean ENTHALPY CHANGE WHEN ONE MOLE OF GASEOUS MOLECULES EACH BREAK one mole of COVALENT BOND in gaseous AVEERAGGED OVER A RANGE OF A COMPOUND
WHAT IS A BORN-HABER CYCLE
THEMOCHEMICAL CYCLE SHOWING ALL THE ENTHALPY INVOLVED INVOLVED IN THE FORMATION OF AN IONIC COMPUND
ENTHALPY CHANGE
ENTHALPY CHANGE IS THE CHANGE IN HEAT AT CONSTANT PRESSURE
STATE WHY ENTHALPY OF FORMATION OF Na(s) IS 0
Na IS AN ELEMENT
STATE WHY ENTHALPY OF FORMATION OF LIQUID Na IS NOT 0
Na(I), I NOT THE STANDARD STATE OF Na
WHAT FACTOR AFFECT THE LATTICE ENTHALPY OF AN IONIC COMPUND
SIZE OF IONS
CHARGE OF IONS
HOW CAN YOU INCREASE THE LATTICE ENTHALPY OF A COMPUND? WHY ?
1.SMALLER IONS: CHARGE CENTRES CLOSE TOGETHER
2. INCREASED CHARGE: GREATER ELECTROSTATIC FORCE OF ATTRACTION BETWEEN OPPOSITELY CHARGED IONS
WHAT IS THE PERFECT IONIC MODEL
ASSUMES IONS ARE PERFECTLY SHPERICAL AND THERE IS AN EVEN CHARGE DISTRIBUTION
WHY IS PERFECTLY IONIC MODEL NOT ACCURATE
IONS ARE NOT PERFECTLY SPHERICAL..
POLARISATION OCCUR WHEN SMALL +VE IONS OR LARGE -VE IONS ARE INVOLVED. COVALENT CHARACTER PRESENT
DEFINE ENTROPY
DISORDER OF A SYSTEM
HIGHER VALUE FOR ENTROPY= MORE DISORDERED
WHAT ARE 2 THINGS TO LOOK OUT FOR TO DECIDE IF ENTROPY INCREASES/DECREASES/STAYS CONSTANT?
NO OF MOLES
SOLID–> LIQUID–>GAS
HOW IS IT POSSIBLE FOR THE TEMPERATURE OF A SUBSTANCE UBDERGOING AND ENDOTHERMIC REACYION TO STAY CONSTANT
HEAT GIVEN OUT TO SURROUNDING
WHAT ARE STANDARD CONDITIONS
100kPa / 1 atm PRESSURE
298K/25C TEMP
HOW COULD A CALORIMETER BE MADE MORE ACCURATE?
ADD LID
INSULATE SIDES OF CALORIMETER
REDUCE DISTANCE BETWEEN FLAME AND BEAKER
WHAT IS AN ENTHALPY OF AN ELEMENT
ENTHALPY OF ALL ELEMENTS IN THEIR STANDARD STATES
WHY MAY EXPERIMENTAL METHODS FOR ENTHALPY DETRMINATION NOT BE VERY ACCURATE?
HEAT LOST TO SURROUNDINGS
NOT IN STANDARD CONDITIONS
INCOMPLETE COMBUSTION
theoretical model:
Model name
type of ions
nature of bonding
Model name: perfect ionic model
type of ions: ions are point charges
nature of bonding: perfectly ionic
experimental model
Model name
type of ions
nature of bonding
Model name: Born Haber
type of ions: ions are polarised
nature of bonding: covalent character
Enthalpy change
Enthalpy change is the change in heat energy at constant pressure
