Multiple Choice
In a molecule of methane (CH_4), what is the approximate value of the bond angles between the hydrogen atoms (labeled 1)?
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12. Molecular Shapes & Valence Bond Theory
Bond Angles
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
What is the approximate value of the bond angle in the molecule CH2O (formaldehyde)?
A
180°
B
109.5°
C
104.5°
D
120°
Verified step by step guidance1
Identify the central atom in the molecule CH2O, which is carbon (C).
Determine the number of regions of electron density around the central atom. In CH2O, carbon is bonded to two hydrogen atoms and one oxygen atom, and there are no lone pairs on carbon, so there are three regions of electron density.
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry based on the number of electron density regions. Three regions of electron density around the central atom correspond to a trigonal planar geometry.
Recall that in a trigonal planar geometry, the ideal bond angles are approximately 120° because the electron pairs repel each other equally and spread out in a plane to minimize repulsion.
Conclude that the bond angle in formaldehyde (CH2O) is approximately 120°, consistent with the trigonal planar shape around the carbon atom.
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