Energetics HL Flashcards
Define ionisation energy
the minimum amount of energy required to remove 1 mole of electrons from 1 mole of gaseous atoms
What type of reaction is the ionisation energy of an element
endothermic reaction (energy is needed to overcome the attraction between the nucleus and the electron)
Define enthalpy of atomisation
the enthalpy change when 1 mole of gaseous atoms is formed from an element in its standard state
What types of reaction is the enthalpy of atomisation
endothermic
What is the general equation of ionisation energy
X(n-1) (g) → X(n)+(g) +e-
What is the general equation of enthalpy of atomisation
X (s) → X (g)
Define lattice enthalpy
the enthalpy change when 1 mole of a solid ionic compound is separated into its gaseous ions under STP
What type of reaction is lattice enthalpy
Exothermic
What is the general equation of lattice enthalpy
XY (s) → X- (g) + S+ (g)
Define electron affinity
the enthalpy change when 1 mole of electrons are added to 1 mole of gaseous atoms
What type of reaction is electron affinity
exothermic
What is the general equation of electron affinity
X(n-1- (g) + e- → X(n)-
Define bond dissociation enthalpy
the enthalpy change when 1 mole of of bonds is broken in the gaseous state
What type of reaction is bond dissociation enthalpy
endothermic
What is the general equation of bond dissociation enthalpy
X2 (g) → 2X (g)
Define enthalpy of solution
the enthalpy change when 1 mole of an ionic substance dissolves in water to give a solution of infinite dilution
Define enthalpy of hydration
the enthalpy change when 1 mole of gaseous ions dissolve in water to give a solution of infinite dilution
The general equation of enthalpy of solution
XY (s) → XY (aq)
The general equation of enthalpy of hydration
X- (g) → X- (aq)
What type of reaction is enthalpy of solution
exothermic or endothermic
What type of reaction is enthalpy of hydration
exothermic
What are the steps to the Born-Haber cycle
1) enthalpy change of atomisation (formation of gaseous atoms from elements)
2) ionisation energy (formation of metal gaseous ions)
3) electron affinity (formation of non-metal gaseous ions)
4) enthalpy of formation
5) lattice enthalpy
What is the equation to find the lattice enthalpy
ΔHlatꝋ = ΔHfꝋ - ΔH1ꝋ
What factors affect lattice enthalpy
- ionic charge
- the size of the ionic radius
Explain why the size of the ionic radius affects the lattice enthalpy
- larger ionic radius decreases the electrostatic attraction in the lattice and result in a more negative (exothermic) lattice enthalpy
Explain the effect of the ionic charge on the lattice enthalpy
An increase in ionic charge, results in a stronger force of electrostatic attraction and leads to a more positive (endothermic) lattice enthalpy
What is the equation enthalpy of solution
ΔHsolꝋ = ΔHlatꝋ + ΔHhydꝋ
What are the factors that affect the strength of the enthalpy of hydration
- the size of the ionic radius (smaller → greater attraction → more exothermic)
- the charge of the ion (greater charge → greater attraction → more exothermic)
What happens when an ionic solid dissolves in water
water is polar, which means it will form ion-dipole bonds with the ions present in the solution
- O2 will be attracted to the positive ions and H2 will be attracted to the negative ions
