Question

Consider the Born-Haber cycle,

Identify I, II, III in the above Born-Haber cycle.

• A. (I)-Electron gain enthalpy (II)-Sublimation enthalpy (III)-Ionisation enthalpy
• B. (I)-Enthalpy of formation (II)-Bond dissociation enthalpy (III)-Enthalpy of transformation
• C. (I)-Lattice enthalpy (II)-Bond dissociation enthalpy (III)-Enthalpy of formation
• D. (I)-Electron gain enthalpy (II)-Bond dissociation enthalpy (III)-Sublimation enthalpy

Answer 1

Answer: (A)

(a) In the given Born-Haber cycle, I, II and III represents respectively as follows :
I. Electron gain enthalpy as one mole of anion being formed from gaseous atoms in its ground state;
i.e. $Cl(g)+e^{-}⟶C{l}^{-}(g)$
II. Enthalpy of sublimation as one mole of vapour formed from the solid,
i.e. $Na(s)⟶Na(g)$
III. Ionisation enthalpy as one mole of an electrolyte completely dissociates into ions,
i.e. $Na(g)⟶N{a}^{+}(g)+e^{-}$