THERMODYNAMICS/ENERGETICS

Question 1

WHAT DOES HESS’S LAW STATE

Answer 1

ENTHALPY CHANGE FOR A CHEMICAL REACTION IS INDEPENDENT OF THE ROUTE TAKEN

Question 2

STANDARD ENTHALPY OF FORMATION

Answer 2

ENTHALPY CHANGE WHEN ONE MOLE OF COMPOUND FORMED FROM IT ELEMENTS UNDER STANDARD STATES (PRODUCTS + REACTANTS)

Question 3

STANDRAD ENTHAPLY OF COMBUSTION

Answer 3

ENTHAPLY CHANGE WHEN ONE MOLE OF A SUBSTANCE IS COMPLETELY BURNT IN EXCESS O2

Question 4

STANDARD ENTHALPY OF ATOMISATION

Answer 4

The enthalpy change when one mole of gaseous atoms are formed from an element in its standard state.

Question 5

1ST IONISATION ENERGY

Answer 5

ENTHALPY CHANGE WHEN ONE MOLE OF e- IS REMOVED FROM ONE MOLE OF GASEOUS ATOMS TO FORM ONE MOLE OF GASEOUS 1+ IONS

Question 6

2ND IONISATION ENERGY

Answer 6

ENTHALPY CHANGE WHEN ONE MOLE OF e- IS REMOVED FROM ONE MOLE OF GASEOUS +1 IONS TO FORM ONE MOLE OF GASEOUS 2+ IONS

Question 7

1ST ELECTRON AFFINITY

Answer 7

ENTHAPLY CHANGE WHEN ONE MOLE OF GASEOUS ATOMS GAINS ONE MOLE OF e- TO FORM ONE MOLE OF GASEOUS 1- IONS

Question 8

2ND ELECTRON AFFIONITY

Answer 8

ENTHAPLY CHANGE WHENONE MOLE OF GASEOUS 1- IONS GAINS ONE MOLE OF e- TO FORM ONE MOLE OF GASEOUS 2- IONS

Question 9

LATTICE ENTHALPY OF FORMATION

Answer 9

ENTHALPY CHANGE WHEN ONE MOLE OF A SOLID IONIC COMPUND IS FORMED FROM ITS GASEOUS IONS

Question 10

LATTICE ENTHALPY OF DISSOCIATION

Answer 10

STAMDARD ENTHALPY CHANGE WHEN ONE MOLE OF SOLID IONIC COMPOUND DISSCOCIATES INTO IOTS GASEOUS IONS

Question 11

ENTHALPY OF SOLUTION

Answer 11

STANDARD ENTHALPY CHANGE WHEN ONE MOLE OF SOLUTE DISSOLVES TO FORM ITS AQUEOUS IONS

Question 12

ENTHALPY OF HYDRATION

Answer 12

STANDARD ENTHALPY CHANGE WHEN ONE OF GASEOUS IONS IS CONVERTED INTO ONE MOLE OF AQEUOUS IONS

Question 13

MEAN BOND DISSOCIATION ENTHALPY

Answer 13

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

Question 14

WHAT IS A BORN-HABER CYCLE

Answer 14

THEMOCHEMICAL CYCLE SHOWING ALL THE ENTHALPY INVOLVED INVOLVED IN THE FORMATION OF AN IONIC COMPUND

Question 15

ENTHALPY CHANGE

Answer 15

ENTHALPY CHANGE IS THE CHANGE IN HEAT AT CONSTANT PRESSURE

Question 16

STATE WHY ENTHALPY OF FORMATION OF Na(s) IS 0

Answer 16

Na IS AN ELEMENT

Question 17

STATE WHY ENTHALPY OF FORMATION OF LIQUID Na IS NOT 0

Answer 17

Na(I), I NOT THE STANDARD STATE OF Na

Question 18

WHAT FACTOR AFFECT THE LATTICE ENTHALPY OF AN IONIC COMPUND

Answer 18

SIZE OF IONS
CHARGE OF IONS

Question 19

HOW CAN YOU INCREASE THE LATTICE ENTHALPY OF A COMPUND? WHY ?

Answer 19

1.SMALLER IONS: CHARGE CENTRES CLOSE TOGETHER
2. INCREASED CHARGE: GREATER ELECTROSTATIC FORCE OF ATTRACTION BETWEEN OPPOSITELY CHARGED IONS

Question 20

WHAT IS THE PERFECT IONIC MODEL

Answer 20

ASSUMES IONS ARE PERFECTLY SHPERICAL AND THERE IS AN EVEN CHARGE DISTRIBUTION

Question 21

WHY IS PERFECTLY IONIC MODEL NOT ACCURATE

Answer 21

IONS ARE NOT PERFECTLY SPHERICAL..
POLARISATION OCCUR WHEN SMALL +VE IONS OR LARGE -VE IONS ARE INVOLVED. COVALENT CHARACTER PRESENT

Question 22

DEFINE ENTROPY

Answer 22

DISORDER OF A SYSTEM
HIGHER VALUE FOR ENTROPY= MORE DISORDERED

Question 23

WHAT ARE 2 THINGS TO LOOK OUT FOR TO DECIDE IF ENTROPY INCREASES/DECREASES/STAYS CONSTANT?

Answer 23

NO OF MOLES
SOLID–> LIQUID–>GAS

Question 24

HOW IS IT POSSIBLE FOR THE TEMPERATURE OF A SUBSTANCE UBDERGOING AND ENDOTHERMIC REACYION TO STAY CONSTANT

Answer 24

HEAT GIVEN OUT TO SURROUNDING

Question 25

WHAT ARE STANDARD CONDITIONS

Answer 25

100kPa / 1 atm PRESSURE 298K/25C TEMP

Question 26

HOW COULD A CALORIMETER BE MADE MORE ACCURATE?

Answer 26

ADD LID INSULATE SIDES OF CALORIMETER REDUCE DISTANCE BETWEEN FLAME AND BEAKER

Question 27

WHAT IS AN ENTHALPY OF AN ELEMENT

Answer 27

ENTHALPY OF ALL ELEMENTS IN THEIR STANDARD STATES

Question 28

WHY MAY EXPERIMENTAL METHODS FOR ENTHALPY DETRMINATION NOT BE VERY ACCURATE?

Answer 28

HEAT LOST TO SURROUNDINGS NOT IN STANDARD CONDITIONS INCOMPLETE COMBUSTION

Question 29

theoretical model: Model name type of ions nature of bonding

Answer 29

Model name: perfect ionic model type of ions: ions are point charges nature of bonding: perfectly ionic

Question 30

experimental model Model name type of ions nature of bonding

Answer 30

Model name: Born Haber type of ions: ions are polarised nature of bonding: covalent character

Question 31

Enthalpy change

Answer 31

Enthalpy change is the change in heat energy at constant pressure