Draw the Lewis structure of H2CO, ?then answer the following questions.
A The electron group geometry of H2CO is
B The molecular shape of H2CO is
C The C-O bond is
D The H-C-H bond angle is approximately
E A H2CO molecule is
The correct answer and explanation is :
Lewis Structure of H₂CO (Formaldehyde)
Formaldehyde (H₂CO) consists of one carbon (C) atom, one oxygen (O) atom, and two hydrogen (H) atoms. Carbon is the central atom, bonded to two hydrogen atoms and one oxygen atom via a double bond.
- Valence Electrons Calculation:
- Carbon: 4 valence electrons
- Oxygen: 6 valence electrons
- Hydrogen: 1 valence electron each × 2 = 2
- Total: 4 + 6 + 2 = 12 valence electrons
- Lewis Structure:
- Carbon forms two single bonds with hydrogen.
- Carbon forms one double bond with oxygen.
- Oxygen has two lone pairs to satisfy the octet rule.
H
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H—C=OAnswers to Questions:
A. The electron group geometry of H₂CO is
Trigonal Planar
The central carbon has three regions of electron density (two single bonds with hydrogen and one double bond with oxygen). According to VSEPR theory, three regions of electron density arrange themselves trigonal planar to minimize repulsion.
B. The molecular shape of H₂CO is
Trigonal Planar
Since there are no lone pairs on carbon, the molecular shape remains the same as the electron group geometry.
C. The C-O bond is
Polar and a double bond
Oxygen is more electronegative than carbon, creating a polar C=O double bond.
D. The H-C-H bond angle is approximately
120°
In a trigonal planar geometry, the ideal bond angles are 120° due to equal repulsion between bonding pairs.
E. A H₂CO molecule is
Polar
The molecule has an asymmetric charge distribution because the C=O bond is polar, and the dipoles do not cancel. Thus, formaldehyde is a polar molecule.
Explanation (300 Words)
The molecular structure of formaldehyde (H₂CO) is determined by valence electrons and VSEPR theory. Carbon forms a double bond with oxygen and two single bonds with hydrogen, using all 12 valence electrons efficiently.
The electron group geometry around carbon is trigonal planar because there are three regions of electron density (C-H, C-H, C=O). Since carbon does not have lone pairs, the molecular shape remains trigonal planar.
The C=O bond is polar, as oxygen is highly electronegative (3.44 on the Pauling scale) compared to carbon (2.55). This electronegativity difference leads to a dipole moment in the molecule. The H-C-H bond angle is approximately 120°, consistent with a trigonal planar structure.
Since oxygen attracts electrons more strongly than carbon, the molecule has an unequal charge distribution, making H₂CO a polar molecule. This polarity affects formaldehyde’s solubility in water and its chemical reactivity.
Formaldehyde is widely used in industry, particularly in resins, disinfectants, and preservatives. Its polarity makes it a good reactant in organic synthesis, as it readily participates in nucleophilic addition reactions.
Thus, the structural and electronic properties of H₂CO determine its chemical behavior, physical properties, and applications.Draw the Lewis structure of H2CO
.