THERMODYNAMICS/ENERGETICS Flashcards

1
Q

WHAT DOES HESS’S LAW STATE

A

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

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2
Q

STANDARD ENTHALPY OF FORMATION

A

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

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3
Q

STANDRAD ENTHAPLY OF COMBUSTION

A

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

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4
Q

STANDARD ENTHALPY OF ATOMISATION

A

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

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5
Q

1ST IONISATION ENERGY

A

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

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6
Q

2ND IONISATION ENERGY

A

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

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7
Q

1ST ELECTRON AFFINITY

A

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

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8
Q

2ND ELECTRON AFFIONITY

A

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

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9
Q

LATTICE ENTHALPY OF FORMATION

A

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

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10
Q

LATTICE ENTHALPY OF DISSOCIATION

A

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

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11
Q

ENTHALPY OF SOLUTION

A

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

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12
Q

ENTHALPY OF HYDRATION

A

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

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13
Q

MEAN BOND DISSOCIATION ENTHALPY

A

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

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14
Q

WHAT IS A BORN-HABER CYCLE

A

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

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15
Q

ENTHALPY CHANGE

A

ENTHALPY CHANGE IS THE CHANGE IN HEAT AT CONSTANT PRESSURE

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16
Q

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

A

Na IS AN ELEMENT

17
Q

STATE WHY ENTHALPY OF FORMATION OF LIQUID Na IS NOT 0

A

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

18
Q

WHAT FACTOR AFFECT THE LATTICE ENTHALPY OF AN IONIC COMPUND

A

SIZE OF IONS
CHARGE OF IONS

19
Q

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

A

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

20
Q

WHAT IS THE PERFECT IONIC MODEL

A

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

21
Q

WHY IS PERFECTLY IONIC MODEL NOT ACCURATE

A

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

22
Q

DEFINE ENTROPY

A

DISORDER OF A SYSTEM
HIGHER VALUE FOR ENTROPY= MORE DISORDERED

23
Q

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

A

NO OF MOLES
SOLID–> LIQUID–>GAS

24
Q

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

A

HEAT GIVEN OUT TO SURROUNDING

25
Q

WHAT ARE STANDARD CONDITIONS

A

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

26
Q

HOW COULD A CALORIMETER BE MADE MORE ACCURATE?

A

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

27
Q

WHAT IS AN ENTHALPY OF AN ELEMENT

A

ENTHALPY OF ALL ELEMENTS IN THEIR STANDARD STATES

28
Q

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

A

HEAT LOST TO SURROUNDINGS
NOT IN STANDARD CONDITIONS
INCOMPLETE COMBUSTION

29
Q

theoretical model:
Model name
type of ions
nature of bonding

A

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

30
Q

experimental model
Model name
type of ions
nature of bonding

A

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

31
Q

Enthalpy change

A

Enthalpy change is the change in heat energy at constant pressure