Chapter 20, Problem 20.139MP

a)

Interpretation Introduction

Interpretation:

The equilibrium concentration of free ${\text{Fe}}^{\text{3+}}$ has to be calculated.

Concept Introduction:

Equilibrium reaction: Chemical equilibrium is the state in which both the reactants and products are present in concentrations which have no further tendency to change with time. The rate of forward reaction is same as the rate of backward reaction.

Formation constant: An equilibrium constant for the formation of a complex in solution.

b)

Interpretation Introduction

Interpretation:

Whether the reaction is nonspontaneous under standard-state conditions has to be stated.

Concept Introduction:

Gibb’s free energy: The energy available to do work and also used to determine the spontaneity of a reaction. The energy released by the overall system.

Relation between Free energy and equilibrium constant:

$\begin{array}{l}{\text{ΔG}}^{\text{o}}\text{=}\text{-}\text{RTln}{\text{K}}_{\text{eq}}\\ \text{where,}\\ {\text{ΔG}}^{\text{o}}\text{is}\text{Gibbs}\text{free}\text{energy,}\\ \text{R}\text{is}\text{constant,}\\ {\text{K}}_{\text{eq}}\text{is}\text{equilibrium}\text{constant}\text{.}\end{array}$

c)

Interpretation Introduction

Interpretation:

The crystal field energy level diagrams for ${\left[\text{Fe}{\left({\text{C}}_{\text{2}}{\text{O}}_4\right)}_3\right]}^{3-}$ has to be drawn, the electron to orbitals has to be assigned, and number of unpaired electrons has to be predicted.

Concept Introduction:

Coordination compounds: The compounds having coordination covalent bonds which form when metal ions react with polar molecules or anions.

Ligands: The ions or molecules that forms coordination covalent bond with metal ions in a coordination compound. Ligands should have minimum one lone pair of electron, where it donates two electrons to the metal. Metal atom accepts the electron pair from a ligand forming a coordination bond.

$Monodentate$ Ligand is ligand which donates only one pair of electrons to form bond with metal. It only makes one bond with metal. Bidentate Ligand is ligand which donates two pair of electrons to form coordinate bond with metal. Polydentate ligand forms two or more coordination bond with metal ions to form a complex.

The strong-field ligands results in pairing of electrons present in the complex and leads to diamagnetic species , while the low-field ligand do not have tendency to pair up the electrons therefore forms paramagnetic species.

Ligand field theory: It is used to explain the bonding between metal and ligand in a coordination complex. Ligand field theory is explained in terms of electrostatic interaction of between metal ion and ligands.

$Spectrochemical$ Series: The list of ligands arranged in an ascending order of $\text{(Δ)}$(the splitting of d-orbitals in presence of various ligands).

$\begin{array}{l}\stackrel{{}^{{\text{I}}^{\text{-}}\text{<}{\text{Br}}^{\text{-}}\text{<}{\text{SCN}}^{\text{-}}\text{<}{\text{Cl}}^{\text{-}}\text{<}{\text{S}}^{\text{2-}}\text{<}{\text{F}}^{\text{-}}\text{<}{\text{OH}}^{\text{-}}\text{<}{\text{O}}^{\text{2-}}\text{<}{\text{H}}_{\text{2}}\text{O}\text{<}{\text{NCS}}^{\text{-}}\text{<}{\text{edta}}^{\text{4-}}\text{<}{\text{NH}}_{\text{3}}\text{< en}\text{<}{\text{NO}}^{\text{2-}}\text{<}{\text{CN}}^{\text{-}}\text{<}\text{CO}}}{\to }\\ {}_{{}^{{}^{\begin{array}{l}\text{weak-field}\text{increasing(Δ)}\text{strong-field}\\ \text{ligands}\text{ligands}\end{array}}}}\end{array}$ The strong field ligands lead to splitting to a higher extent than the weak field ligands and the wavelength of light absorbed depends on the energy gap that is produced by a particular ligand.

The five d orbitals get divided into two sets that are ${\text{d}}_{\text{xy}}{\text{, d}}_{\text{yz}}{\text{ and d}}_{\text{xz}}$ orbitals forms one set and ${\text{d}}_{{\text{x}}^{\text{2}}{\text{-y}}^{\text{2}}}{\text{and d}}_{{\text{z}}^{\text{2}}}$ forms another set. The first set are oriented between the x, y and z axes whereas the second set gets oriented along the axis.

d)

Interpretation Introduction

Interpretation:

The complex ${\left[\text{Fe}{\left({\text{C}}_{\text{2}}{\text{O}}_4\right)}_3\right]}^{3-}$ structure has to be drawn; whether the complex ${\left[\text{Fe}{\left({\text{C}}_{\text{2}}{\text{O}}_4\right)}_3\right]}^{3-}$ is chiral or achiral has to be explained.

Concept Introduction:

Achiral: A molecule is achiral if it is superimposable on its mirror image. Most achiral molecules do have a plane of symmetry or a center of symmetry.

Chiral: A molecule is chiral if it is non superimposable on its mirror image. Most chiral molecules can be identified by their lack of a plane of symmetry.