Chemistry Gases BUMHS 2024
PMDC Verified Question 13 of 65
Inter molecular repulsive forces in gases are due to:
A
Ionic bonding
B
Vander Waal's forces
C
Dipoles
D
Covalent bonding
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Vander Waal's forces
Concept:

Real gases experience both attractive and repulsive intermolecular forces, which cause them to deviate from ideal behavior under varying conditions of pressure and temperature.

Solution:

  • The broad category of non-covalent, non-ionic interactions between molecules is collectively referred to as van der Waals forces.


  • While usually discussed in terms of attraction (like London dispersion forces), the van der Waals equation (\( (P + a/V^2)(V - nb) = RT \)) also accounts for repulsive forces at very short ranges via the 'b' constant (excluded volume).


  • When gas molecules are forced incredibly close together, their electron clouds experience Pauli repulsion. In the context of real gas terminology, both these attractive and repulsive intermolecular phenomena fall under the umbrella of van der Waals interactions.


Why other options are incorrect:

  • Options A & D: Ionic and covalent bonds are strong intramolecular forces that hold atoms together within a compound, not forces between separate gas molecules.
  • Option C: Dipoles are a specific type of attractive van der Waals force, but they do not account for the fundamental short-range repulsion experienced by all gases (even non-polar ones).

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