Thermodynamics Flashcards
Define enthalpy of formation
Endo or exo
Enthalpy change when one mol of a substance is formed from its elements with all substances in their standard states and under standard conditions
Exothermic
Define enthalpy of atomisatuon
Endo or exo
Enthalpy chnage when one mol of gaseous atoms are formed from the elements in its standard states under standard conditions
Endothermic
Define bond dissociation enthalpy
Endo or exo
Enthalpy chnage to break one mole of a specific bond in the gas phase
Endo
What is the relationship between bde and atomisation for diatomic molecules
The bde is half the atomisation
Bde = 2x atomisation
Define enthalpy of first ionisation energy
Endo or exo
Enthalpy change when u mole of electrons is removed from I mole of gaseous atoms to form one mole of gaseous ions with +1 charge
Exithermic
Define enthalpy do second ionisation
Endo or exi
The enthalpy change when I mole of electrons is removed from one mole of gaseous ions with +1 charge to form one mole gaseous 2+ ions
Endothermic
Define enthalpy of first electron affinity
Endo or exo
Enthalpy change when I mole of electrons added to one mole gaseous atoms to form on mole gaseous ions with -1 charge
Exothermic
Define enthalpy of second electron affinity
Exo or Endo
Enthalpy change when I mole of electrons is added to one mole of gaseous ions with a -1 charge to form 1 mole of gaseous ions it’s a 2- charge
Endo
Define enthalpy of lattice formation
Endo or exo
Enthalpy change when I mole of a solid ionic compound is formed from its gaseous ions
Exo
Define enthalpy of lattice dissociation
Endo or exo
Enthalpy when 1 mole of a solid ionic compound is broken down into its gaseous ions
Endo
What is the relationship between enthalpy of lattice formation and enthalpy of lattice dissociation
They are the same magnitude just different signs
What 2 factors influence the magnitude of lattice enthalpy
Charge of the ion
Size of ion
How does charge of ion affect magnitude of lattice enthalpy
Bigger charge means stronger attraction
How does size of ion affect magnitude of lattice enthalpy
Bigger ion is weaker attraction
What are 2 assumptions of the perfect ionic model
In jons are perfectly spherical
Charge is evenly distributed
What 2 factors increase covalent character in an ionic substance
Positive ions - bigger charge density is more covalent character
Negative ions - bigger negative ion more likely to have higher covalent character
How does the covalent character in bonds affect the strength
More is stronger bonds
Define standard enthalpy of solution
Enthalpy change when 1 mole of solid ionic compound is dissolve into water to produce aqueous ions
Define standard enthalpy hydration
Enthalpy change when I mole of gaseous ions is converted to one mole aqueous ions
What forces from between negative and positive ions and water when they are hydrated
Ion dipole forces
What process is enthalpy of hydration and why
Exo
Form attraction between ions and water
What 2 factors affect magnitude of enthalpy of hydration
Charge of ion - bigger is stronger
Size of ion - maker is stronger
Hess cycle for enthalpy of solution and hydration
Photos
What is entropy
Units
Symbol
A measure of disorder
S
J/k
Standard conditions for measuring entropy
100kpa
298k
How do you calculate entropy change
Sum fo entropy products - sum of entire reactants
What is a feasible reaction
A spontaneous recation occurring
Gibbs free energy equation
Delta g = delta H - t x delta s
Units for Gibbs freee
Kj / mol
How to convert from j/k to kj/k
Divide by 1000
Convert before doing equation
Negative enthalpy
Positive entropy
Name effect on g
What is graph like
Feasible at all temperatures
Photo
Positive enthalpy
Negative entropy
Effect on Gibbs
Graph
Reaction never feasible at any temperature
Positive entropy
Positive enthalpy
Effect on Gibbs
Graph
Reaching feasible at high temperatures
Negative enthalpy
Negative entropy
Effect on g
Graph
Reaction feasible at low temperatures
Gibbs free energy equation as equation of straight line
Delta g is why
T is x
-delta s is gradient
Delta h is y intercept
What does the value it crosses x axis mean
temperature reaction ether starts or stops being feasible
