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enthalpy of formation definition
the enthalpy change when 1 mol of a compound is formed from its constituent elements under standard conditions. All reactants and products in standard states
enthalpy of combustion definition
the enthalpy change when 1 mol of a substance completely burns under oxygen under standard conditions. All reactants and products in standard states
enthalpy of reaction definition
the enthalpy change when a reaction occurs in the molar quantities shown in the chemical equation. All reactants and products in standard states
enthalpy change of neutralisation
the enthalpy change when an alkali and acid react to form 1 mol of water under standard conditions
Enthalpy definition
the heat energy change of a substance under constant pressure
the enthalpy of atomisation
the enthalpy change when 1 mol of gaseous atoms is formed from its constituent elements under standard conditions
first ionisation energy
the energy required to form 1 mol of gaseous unipositive ions from 1 mol of gaseous atoms under standard conditions
second ionisation energy
the energy required to form 1 mol of gaseous dipositive ions from 1 mol of gaseous unipositive ions
first electron affinity
the enthalpy change when 1 mol of gaseous atoms each gain an electron to form 1 mol of gaseous uninegative ions under standard conditions
second electron affinity
the enthalpy change when 1 mol of gaseous uninegative ions each gain an electron to form 1 mol of gaseous dinegative ions under standard conditions
enthalpy change of solution
the enthalpy change when 1 mol of a solute dissolved by a solvent under standard conditions
enthalpy change of hydration
the enthalpy change when 1 mol of gaseous ions dissolved in water to form 1 mol of hydrated ions
enthalpy of lattice formation
the enthalpy change when 1 mol of a solid ionic compound formed from its constituent ions in the gaseous phase under standard conditions
enthalpy of lattice dissociation
the enthalpy change when 1 mol of a solid ionic compound broken down to its constituent ions in the ions in gaseous phase under standard conditions
why does magnesium ion have a greater hydration enthalpy than sodium ion
magnesium is a smaller ion and has a greater charge
so higher charge density than sodium ion
so attracts water more strongly
(delta- oxygen)
in terms of electrostatic forces determine why electron affinity has a negative value
electrostatic force of attraction between nucleus and external electron
energy released when electron added
what 2 factors make up the perfect ionic model
perfectly spherical
only electrostatic force of attraction between ions/no covalent character
what type of value does born haber depict for enthalpies
experimental value
why is there a difference between theoretical and experiemnetal enthalpies
as ionic lattice has covalent character
gibbs equation
gibbs free energy = enthalpy change - temp x entropy of system
gibbs energy =
-temp x entropy total
temperature where feasible =
enthalpy change / entropy of system
reaction is feasible when
temperature below 0
why is the entropy 0 at 0K, state in terms of molecules
at 0K molecules have no energy
so no disorder of molecules
why does the graph slope upwards from the origin
as Temperature increases, entropy increases
explain with the aid of a thermodynamical equation how free gibbs energy can be shown by a line
use whiteboard
state equation
state which parts coorespond ot y=mx+c
why is the evaporation of water spontaneous even though it is endothermic
molecules more disorded when water evaporate
positive entropy change
TdeltaS > deltaH
deltaG < 0
what is entropy?
the measure of disorder
calculate entropy
products entropy - reactants entropy
as temperature increases…
entropy increases and disorder increases
feasible is interchangeable with…
spontaneous
label all parts of a free gibbs energy graph
free gibbs energy - y-axis
temperature - x-axis
-entropy of system - gradient