Chemistry Thermochemistry PMDC 2020
PMDC Verified Question 55 of 81
Born-Haber cycle is used to determine the lattice energies of:
A
Covalent solids
B
Metallic solids
C
Ionic solids
D
Molecular solids
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Ionic solids
Concept:

The Born-Haber cycle is an application of Hess's Law designed specifically to analyze the thermochemical steps involved in forming crystal lattices from charged particles.

Formula:

$$ \Delta H_{\text{lattice}} = \Delta H_f - \Sigma (\text{ionization}, \text{electron affinity}, \text{etc.}) $$

Solution:

  • The cycle relies on measuring ionization energies (to form cations) and electron affinities (to form anions).


  • These discrete charged gaseous ions then condense to form a solid lattice.


  • This exact mechanism of cation-anion electrostatic attraction strictly defines the formation of Ionic solids (e.g., NaCl, KBr).


Why other options are incorrect:

Covalent, metallic, and molecular solids are held together by covalent bonding, metallic "sea of electrons", and intermolecular forces respectively, which do not fit the cation-anion formation model of the Born-Haber cycle.

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