Chemistry Chemical Bonding MDCAT 2012
PMDC Verified Question 98 of 102
The angle between un-hybridized p-orbital and three \( \text{sp}^2 \) hybrid orbitals of each carbon atom is:
A
120°
B
109.5°
C
90°
D
180°
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: 90°
Concept:

In \( \text{sp}^2 \) hybridization, three hybrid orbitals form a planar trigonal structure, and the remaining unhybridized p-orbital is situated perpendicular to this plane.

Formula:

$$ \text{sp}^2 \text{ plane} \perp \text{unhybridized } p_z \text{ orbital} $$

Solution:

  • The three \( \text{sp}^2 \) hybrid orbitals arrange themselves in a flat plane with 120° angles between them.


  • The unhybridized p-orbital (which will be used to form a pi bond) stands straight up and down, piercing the center of this plane.


  • Thus, the angle between the flat plane (the hybrid orbitals) and the unhybridized p-orbital is exactly 90°.


Why other options are incorrect:

  • Option A: 120° is the angle between the \( \text{sp}^2 \) hybrid orbitals themselves.
  • Option B & Option D: Correspond to tetrahedral and linear geometries, respectively.

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