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A-level Chemistry

Could anyone explain born-haber cycles to me?
I cannot understand it no matter how much I try





😭
(edited 8 months ago)
Original post by dumb-problem
Could anyone explain born-haber cycles to me?
I cannot understand it no matter how much I try
😭
firstly, some definitions:
Lattice enthalpy - enthalpy change when 1 mole giant ionic compound is formed from its gaseous ions.
Enthalpy change of formation - 1 mole of compound formed from its elements at standard state.
Enthalpy change of atomisation - 1 mole of gaseous atom formed from its element in standard state.
Ionisation energy - energy required to remove 1 mole of electrons from 1 mole of __.
Electron affinity - energy to add 1 mole of electron to 1 mole of __ (first is exothermic. Successive is endothermic due to repulsion).

A born haber cycle links these together.
So imagine pathway 1: Ca(s) + Cl2 (g) -> CaCl2(s) which is enthalpy change of formation.
Pathway 2 (to get to the same CaCl2(s)) would be:
Enthalpy change of atomisation of Cl2 to Cl and Ca(s) to Ca(g)-> ionisation energy to make Ca to Ca2+ -> enthalpy change of electron affinity (for 2 Cl to become Cl-) -> now finally lattice enthalpy to make Ca+(g) + Cl-(g).

So I like to start from making the equation for enthalpy change of formation. Then: using atomisation to make the species (g) -> using ionisation to form negative ions and electron affinity to make positive ions -> then use lattice enthalpy.

Another born haber cycle.
Definitions:
Enthalpy change of solution: 1 mole of giant ionic lattice dissolved in water to make (aq) ion.
Enthalpy change of hydration: 1 mole of (g) ions dissolved in water to make (aq) ion.
So can you see the link between lattice enthalpy [ (g) ion -> giant ionic lattice], with solution [giant ionic lattice -> (aq) ion] and hydration [ (g) ion -> (aq) ion] to make a cycle.

I will add picture. Can you see how the enthalpy definitions (formation, atomisation, ionisation, electron affinity, lattice enthalpy) link together in (1) and how (lattice enthalpy, solution, hydration) link together in (2)?
IMG_5695.jpeg
(edited 8 months ago)
Original post by dumb-problem
Could anyone explain born-haber cycles to me?
I cannot understand it no matter how much I try
😭

Check this video out

There are also Born-Haber videos on MgO, Na2O and MgCl2 on the same channel.

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