When oxalate anions, C₂O₄²⁻, are added to a solution of [Fe(H₂O)₆]³⁺, the formation of [Fe(C₂O₄)₃]³⁻ occurs in a series of steps that together result in the following overall reaction:[Fe(H₂O)₆]³⁺(aq) + 3 C₂O₄²⁻(aq) → [Fe(C₂O₄)₃]³⁻(aq) + 6 H₂O(l)During the first step of the reaction, two new coordinate bonds are formed to produce an intermediate ion of:

Question

Quizplus · Accepted Answer

11ecba2d_11f4_e748_a3bf_4728313b28df_MD0008_00 Complex ions (coordination complexes) consist of a central metal ion surrounded by one or more ions or molecules called ligands that are bound to the metal center by coordinate bonds. The coordinate bonds form because the ligands surrounding the metal center act as Lewis bases and donate a lone pair of electrons to the metal center, which acts as a Lewis acid. These Lewis acid-base coordinations hold the complex together, but stronger Lewis bases can displace weaker Lewis bases as ligands within the complex. In the [Fe(H₂O)₆]³⁺ complex ion, an uncharged water molecule serving as a ligand is a weak Lewis base and can be displaced by the oxalate (C₂O₄²⁻) anion, a stronger Lewis base. Each C₂O₄²⁻ anion displaces two water molecules and decreases the overall charge of the resulting complex ion by −2. Displacement of water within the complex occurs in a stepwise sequence. In the first step, two water molecules are displaced from [Fe(H₂O)₆]³⁺ by a single C₂O₄²⁻ anion to form an intermediate complex ion: [Fe(H₂O)₆]³⁺(aq) + C₂O₄²⁻(aq) → [Fe(H₂O)₄(C₂O₄)]⁺(aq) + 2 H₂O(l) In the second and third steps, additional C₂O₄²⁻ anions displace the remaining water ligands to form the final product. (Choice B) This is the intermediate ion formed during the second step of the reaction, not the first step. (Choice C) This is not an intermediate ion; it is the end product formed during the final third step of the overall net reaction. (Choice D) Both the ion charge and this formula are incorrect. The first step adds one C₂O₄²⁻ ion to the complex, but each oxalate ion displaces two water molecules and decreases the overall charge of the complex by −2. Educational objective: When a reaction occurs in a stepwise sequence, the species formed as products in earlier steps and then subsequently consumed as reactants in later steps are intermediate species. Intermediates do not appear in the overall net reaction.

When Oxalate Anions, C2O42−, Are Added to a Solution of [Fe(H2O)6]3+

When Oxalate Anions, C₂O₄²⁻, Are Added to a Solution of [Fe(H₂O)₆]³⁺