Oxalate ion and carbon dioxide: Draw Lewis structures for the oxalate ion and for carbon dioxide 1.

Oxalate ion and carbon dioxide: Draw Lewis structures for the oxalate ion and for carbon dioxide 1. Estimate the angles and name the shapes : around the carbon atoms in both b. molecules. C. What is the length of each ofthe carbon-oxygen bonds? What happens at the molecular level during the reaction of: C202- 7 2 COz? d.

The Correct Answer and Explanation is:

. Lewis Structures:

1. Oxalate ion (C₂O₄²⁻):
   Each carbon atom in the oxalate ion is bonded to two oxygen atoms. The structure has resonance, meaning multiple valid Lewis structures can exist. Each carbon is bonded to one oxygen by a double bond and to another by a single bond with a negative charge. The negative charges are delocalized over the four oxygen atoms.

mathematicaCopyEdit   O⁻       O⁻
    \       /
     C == C
    /       \
   O⁻       O⁻

Note: In proper resonance structures, the double bonds shift positions across the four oxygen atoms.

2. Carbon dioxide (CO₂):
   CO₂ is a linear molecule with two double bonds between carbon and oxygen.

mathematicaCopyEditO == C == O

b. Molecular Shapes and Bond Angles:

• Oxalate ion (C₂O₄²⁻):
  Each carbon is bonded to three atoms (2 oxygens and 1 carbon), and there are no lone pairs on carbon, so the geometry around each carbon is trigonal planar.
  Bond angles are approximately 120°.
• Carbon dioxide (CO₂):
  The carbon is bonded to two oxygen atoms and has no lone pairs, leading to a linear shape.
  Bond angle is 180°.

c. Carbon-Oxygen Bond Lengths:

• In oxalate ion, due to resonance, each carbon–oxygen bond is intermediate between a single and a double bond. The average bond length is about 1.25 Å, which is between the typical C–O single bond (~1.43 Å) and C=O double bond (~1.20 Å).
• In carbon dioxide, the C=O double bonds are well-defined with a bond length of about 1.16 Å.

d. Reaction and Molecular Changes:

The reaction:

mathematicaCopyEditC₂O₄²⁻ → 2 CO₂

During this reaction, the oxalate ion undergoes decomposition into two molecules of carbon dioxide. At the molecular level, the C–C bond in oxalate breaks, and each carbon forms a double bond with two oxygen atoms, producing two CO₂ molecules. This results in a change in both bonding and geometry:

• The carbon hybridization changes from sp² (in oxalate) to sp (in CO₂).
• The electron delocalization in oxalate is replaced by localized double bonds in carbon dioxide.
• Energy is released during the formation of the stable CO₂ molecules.

This transformation is important in biological and environmental chemistry, especially in metabolic and geochemical cycles involving oxalates and carbon dioxide.