Question
Draw the Lewis structure for formic acid. Which of the following statements is FALSE?(a) Bonding-electron count: 10.(b) Bond multiplicities: three single; one double.(c) Nonbonding-electron pairs: four.(d) Carbon hybridization: sp².(e) σ/π bond counts: 3/1.
CH₂O₂ Lewis structure: formic acid
The false option is (e). Formic acid has four σ bonds and one π bond, not three σ bonds and one π bond.
Each pair of dots is a lone pair. Both oxygens have two lone pairs. The upper oxygen forms C=O; the other oxygen forms the C–O and O–H single bonds. One hydrogen attaches to carbon and the other to oxygen.
Electron count and formal charges
The formula gives 4 + 2(1) + 2(6) = 18 valence electrons. Three single bonds use six electrons and one double bond uses four. The remaining eight electrons form four lone pairs. Thus 10 bonding + 8 nonbonding = 18.
Carbon has four bonding pairs and no lone pairs, so its formal charge is 4 − 0 − 4 = 0. For either oxygen, 6 − 4 − 2 = 0. Each hydrogen has formal charge 1 − 0 − 1 = 0. Carbon and both oxygens have octets; each hydrogen has a duet.
Evaluate all five options
| Option | Verdict | Check against the structure |
|---|---|---|
| (a) | True | Three single bonds plus one double bond contain 3(2) + 4 = 10 shared electrons. |
| (b) | True | C–H, C–O, and O–H are single; the other C–O connection is double. |
| (c) | True | Two lone pairs on each oxygen give four in total. |
| (d) | True | Three bonding directions around carbon correspond to sp² hybridization in the valence-bond model. |
| (e) | False | Each of the four connected atom pairs supplies one σ bond; the second component of C=O supplies one π bond. |
Why the name matters
The question specifies formic acid, which fixes the H–C(=O)–O–H connectivity. A molecular formula alone lists atom counts, not a unique bonding arrangement. Moving a hydrogen to create a different connectivity does not produce a resonance form of formic acid. The neutral structure shown is the usual principal Lewis contributor; this task does not ask for an exhaustive set of resonance contributors.
Evidence boundary
The source is Texas A&M CHEM 101, Spring 2001, Exam 3 Form A, question 21&22. All five options are retained in equivalent compact wording with unchanged values and order. The named species is formic acid, not an unspecified CH₂O₂ isomer; the diagram is schematic, and the answer evaluates the supplied options rather than reporting measurements.
Sources
These references support the concepts and methods used in the explanation above.