# Thermodynamics

Define lattice formation enthalpy
1 mole of solid ionic compound s formed from its gaseous ions
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Define lattice dissociation enthalpy
1 mole of a solid ionic compound is completely dissociated into its gaseous ions
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Define enthalpy change of atomisation of an element
1 mole of gaseous atoms is formed from an element in its standard states
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Define first ionisation energy
1 mole of gaseous 1+ ions is formed from 1 mole of gaseous atoms
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Define first electron affinity
1 mole of gaseous 1- ions is made from 1 mole of gaseous atoms
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Define enthalpy change of hydration
1 mole of aqueous ions is formed from gaseous ions
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Define enthalpy change of solution
1 mole of an ionic substance dissolves in enough solvent to form an infinitely dilute solution (there is no change in concentration)
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What useful acronym can be used to remember the order of Born-Haber cycles?
FAIEL
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What does the purely ionic model assume?
Assumes that all ions are spherical, and have their charge evenly distributed
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Why us experimental lattice enthalpy data different from actual data?
Because most ionic compounds have covalent character and aren't wholly spherical
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What is entropy?
Entropy tells you how much disorder there is, represented by S
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Which state has the lowest entropy and which has the highest?
Solids have the lowest and gases have the highest
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Dissolving a solid does what to the entropy?
Increases the entropy
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How do you calculate entropy change?
S= S products -S reactants
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What is free energy change ?
A measure used to predict whether a reaction is feasible and carry on to completion without any energy being supplied to it
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When is a reaction feasible?
When G is negative or equal to zero
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How do you calculate free energy change (G) ?
G = H - TxS
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If a reaction is exothermic and has a positive enthalpy...
...G is always negative and feasible at any temperature
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If a reaction is endothermic and has a negative entropy change...
...G is always positive and reactions are not feasible
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If H is positive and S is positive....
....the reaction will only be feasible above a certain temperature
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If H is negative and S is negative...
...the reaction will only be feasible below a certain temperature
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How do work out the temperature when a reaction is feasible?
T = H/S
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So on a graph where G is the y-axis and T is the x-axis...
...the gradient of the line is equal to -S and the y-intercept is equal to H
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## Other cards in this set

### Card 2

#### Front

Define lattice dissociation enthalpy

#### Back

1 mole of a solid ionic compound is completely dissociated into its gaseous ions

### Card 3

#### Front

Define enthalpy change of atomisation of an element

### Card 4

#### Front

Define first ionisation energy

### Card 5

#### Front

Define first electron affinity