Q10.88 CP - Chemistry: Molecular Nature Of Matter And Change

Question

Oxalic acid (${\mathbf{H}}_{\mathbf{2}}{\mathbf{C}}_{\mathbf{2}}{\mathbf{O}}_{\mathbf{4}}$ ) is found in toxic concentrations in rhubarb leaves. The acid forms two ions, ${\mathbf{HC}}_{\mathbf{2}}{{\mathbf{O}}_{\mathbf{4}}}^{\mathbf{-}}$ and ${\mathit{C}}_{\mathbf{2}}{{\mathit{O}}_{\mathbf{4}}}^{\mathbf{2}\mathbf{-}}$ , by the sequential loss of H ions. Draw Lewis structures for the three species, and comment on the relative lengths and strengths of their carbon-oxygen bonds. The connections among the atoms are shown below with single bonds only.

Step-by-Step Solution

Answer

The Lewis structure of (3) three species.

1. Oxalic acid has two longer C-O bonds and two shorter C=O bonds. The C-OH bond is longer than C=O bond and C=O bond is stronger than C-OH bond.

2. H atom has one long and weaker C-O bond and the other 3 are are short and stronger C=O bond in the  ${\text{HC}}_{\text{2}}{{\text{O}}_{\text{4}}}^{\text{ - }}$. The bond order is 1.5.

3. All C-O bonds are of equal bond length and strength in  $C_2{O_4}^{2-}$. The bond order of each is 1.5.

Step 1: Definition

Lewis structures, also known as electron-dot structures or electron-dot diagrams, are diagrams that display the interactions between the atoms in a molecule as well as any potential lone pairs of electrons.

Step 2: The Lewis structure of (3) three species.

Step 4: The relative lengths and strengths of their carbon-oxygen bonds:

1. 
   

Resonance structures are collections of Lewis structures that explain how electrons in a molecule are delocalized.

1. Oxalic acid is the simplest dicarboxylic acid. It has two C=O and two C-OH bonds. On the oxygen atoms of the carbonyl and hydroxyl groups, there are two lone pairs. Oxalic Acid has two longer C-O bond and two shorter C=O bond.

2. Due to resonance the side of the molecule with H atom have one long CO bond and 1 short C=O bond. On the other side the bond lengths are smaller than the other side. The bond order is 1.5. Resonance structures of ${\text{HC}}_{\text{2}}{{\text{O}}_{\text{4}}}^{\text{ - }}$are as follow

      c. All the carbon-oxygen bonds are of equal bond length. The bond order of each is 1.5. The            resonance structures of $C_2{O_4}^{2-}$ are as follows.