Thermodynamics Flashcards
On a born- Hager cycle which way is exothermic
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On born-haber cycle which way is endothermic
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On born hacker cycle which way is up
Endothermic
On born-Hager cycle which way is down
Exothermic
What is the equation for Enthalpy of formation
Enthalpy of formation = sum of everything else
How does lattice Enthalpy change down a group
Gets less negative
How does size of ion affect lattice formation
The larger the ion, the less negative the eight alloy of lattice formation
Why do larger ions have a less negative Enthalpy of lattice formation
Charges of larger ions are further apart, so weaker electrostatic force of attraction between them
How does a bigger ionic charge affect Enthalpy
More negative, stronger Enthalpy
What is the perfect ionic model used for
Predicting theoretical lattice enthalpies
What are the assumptions for the perfect ionic model
- ions are 100% ionic
- ions are spherical
- attractions are purely electrostatic
Why are there some discrepancies between experimental and theoretical values of lattice formation
The bond has some covalent character
Which is bigger, born Haber value or theoretical value of lattice formation
Born haver value»_space; theoretical value
When do ions have a tendency towards covalent character
- +ve ion is small and has multiple charges
- -ve ions is larger and has multiple charges
What is a spontaneous process
Will proceed on its own without any external influence
Define entropy
The concept of increasing disorder
What determines whether a reaction is feasible
The balance between entropy and Enthalpy
What is the reaction for Gibbs’s free energy
G = H -T(S)
What is the equation for entropy S
Sum S (products) - Sum S (reactants)
What is the unit for entropy
J mol^-1 K^-1
What must delta G be for a reaction to be feasible
Negative or 0
What is delta G for physical state changes
Zero due to equilibria
Define Enthalpy of solution
The standard Enthalpy change when 1 mole of an ionic solid dissolves in a large enough amount of water that the dissolved ions are well separated and do not interact with each other
Define Enthalpy change of hydration
The Enthalpy change when one mole of gaseous ions becomes aqueous ions
Is enthalpy of hydration reaction endo or exothermic
Exothermic reaction as bonds are made between ions are water molecules
Why are ions attracted to water molecules
- +ve ions are attracted to s+ hydrogen on polar water molecules
- -ve ions are attracted to s- oxygen on polar water molecules
What is the relationship between charge density and hydration Enthalpy
The higher the charge density, the greater the hydration enthalpy
When is a substance more likely to be soluble
If Hsol is exothermic
When is a substance insoluble
If lattice enthalpy»_space; hydration , so Hsol is exothermic
Define Enthalpy of formation
When 1 mole of a compound is formed from its constituent elements under standard conditions, 100KPa and 273K, with all reactants and products being in their standard states
Define enthalpy if atomisation
Enthalpy change when 1 mole of gaseous atoms is formed for the element in its standard state
Define bond dissociation enthalpy
The standard molar Enthalpy change when 1 mole of covalent bond is broken into two gaseous atoms
