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alevel chem year 2 > Enthalphy and Entropy > Flashcards

Enthalphy and Entropy Flashcards

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1
Q

Lattice enthalpy

A

Enthalpy change accompaigning the formation of one mole of an ionic compound from its gaseous ions under standard conditions

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2
Q

Enthalpy change of formation

A

When one mole of a compound is formed from its consituent elemtns in their standard states under standard conditions

IONIC COMPOUND

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3
Q

Enthalpy change of atomisation

exo or endo

A

One mole of gaseous atoms fores under the element in its standard state
ENDOTHERMIC -bonds broken to form gaseous atoms

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4
Q

First ionisation energy

A

The enthalphy change accompanying removal of one electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions

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5
Q

Second ionisation energy

A

The removal of 1 electorn from each ion in 1 mole of gaseous 1+ ions to form one mole of gaseous 2+ ions

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6
Q

IS IONISATION energy endo or exo

A

ENDO

energy required to overcome attraction between negtive electron and nucleus

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7
Q

First electron affinity

A

The addition of 1 electron to each atom in one mole of gasoeus atoms to form one mole of gaseous 1- ions

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8
Q

Second electron affinity

A

Addition of 1 electron to each ion in one mole of gaseous 1_ ions to form 1 mole of gaseous 2- ions

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9
Q

1st electron affinity endo or eXO

A

exo

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10
Q

2nd electron affinity endo or exo

A

ENDOTHERMIC
2nd electron is being gained by negative ion, which repels electron away
energy must be put into force the negative charged eletron ont the negative ion

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11
Q

Lattice enthalpy
exo or endo
what is it actually measuring

A 
Solid ionic compounds tend to be VERY stable 
Strong electrostatic
Energy barrier to break down 
Strength of ionic bonding 
EXOTHERMIC
negative
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12
Q

Route 1 to forming the ionic lattice

3 steps

A

Formation of gaseous atoms
- EXOTHERMIC bond breaking

Formation of gaseous ions

Lattice formation
- Solid ionic clattice
Lattice enthalphy
Exothermic

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13
Q

Route 2 to forming the ionic lattice

1 step

A

Elements in their standard states DIRECLTY to ionic lattice

Formation
EXOTHERMIC

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14
Q

Enthalphy change of formation ( working out )

A

Adding all the other energy changes together

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15
Q

Enthalphy change of solution

A

One mole of solute dissolves in a solvent

Can be exo or endo

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16
Q

q=

A

mc change in t

17
Q

The dissolving process - 2 steps

A

Ionic lattice is broken forming seperate gaseous ions

Seperate ions interact with polar water molecules to form hydrated aqeuous ions - hydration

18
Q

Enthalphy change of hydration

A

The enthalpy change that takes place when one mole of isolated gaseous ions dissolve in water forming 1 mole of aqueous ions under standard conditions

gaseous — aqueous

19
Q

Factors affecting lattice enthalphy /hydration ?

A

ION SIZE

  • Greater
  • Ionic radius increases
  • attraction decreases
  • Lattice enthalpy less negative
  • melting point decreases
IONIC CHArGE 
- Increases 
Attraction increases
- lattice energy more negative 
- MP increases
20
Q

When will a compound definitely dissolve

A

If exothermic

Hydration enthalpies lager then lattice enthalpy

21
Q

What is entropy

A

S
Disorder in a system
jk -1 mol -1

22
Q

greater entropy

A

Higher energy spread perkelvin per mole

23
Q

If a system becomes more random

A

Entropy change POSITIVE

24
Q

if a system become less random

A

Entropy change is NEGATIVE

25
Q

reactions that produce gases? Entropy effect

4 moles of gas — 2 moles of gas

A

Increase in entropy

Decrease- negative entropy change

26
Q

Standard entropy

A

The entropy of a substance under standard conditions
100kPa, 298k
Jk-1mol-1
POSITIVE

27
Q

Entropy change of a reaction

A

Sum of products - reactants

28
Q

Free energy ?

A

overall energy change in a reaction

made up of 2 types of energy

29
Q

2 types of energy making up free energy

A
  1. The enthalphy change(H), the heat transfer between teh chemical system and surroundings
  2. The entropy change at the temperature of the ssytem
    T change in S .
    Dispersion of enregy within the chemcial system
30
Q

Gibbs equation

A

< G =

31
Q

Enthalpy H units

A

kJ mol-1

32
Q

Temp units

A

K

33
Q

Entropy S units

A

JK-1mol-1

34
Q

Feasibilitity of a reaction ?

A

Free energy <0 ( exothermic)

for reaction to happen

35
Q

Limitations for feasibiltiy

A

Doesnt take into account of kinetics or rate of reaction

Indicates thermodynamic feasbility

alevel chem year 2 (7 decks)

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