Multiple Choice
In the actual molecule of water (H_2O), which has a bent geometry, what are the approximate values of the bond angles a (H–O–H) and b (O–H–lone pair)?
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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 value of the bond angle in the molecule COH2 (formaldehyde)?
A
120^ext{o}
B
180^ext{o}
C
104.5^ext{o}
D
109.5^ext{o}
Verified step by step guidance1
Identify the central atom in the molecule COH2 (formaldehyde), which is the carbon atom (C).
Determine the number of regions of electron density around the central carbon atom. In formaldehyde, carbon is bonded to two hydrogen atoms and one oxygen atom, making a total of 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 between the atoms are approximately 120 degrees because the electron pairs repel each other equally in a plane.
Conclude that the bond angle in formaldehyde (COH2) is close to 120 degrees, consistent with the trigonal planar shape predicted by VSEPR theory.
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