What is meant by the term stability constant, K_stab?

The table below shows values of the stability constants for the following equilibrium:

[M(H₂O)₆]ⁿ⁺_(aq) + L^-_(aq) ⇌ [M(H₂O)₅L]^(n-1)+_(aq) + H₂O_(l)

where M is one of the metal ions listed and L is one of the ligands which replaces one H₂O molecule.

Use the data in the table to predict the formula of the complex formed in the greatest amount when a solution containing equal concentrations of both Cu²⁺ and Ni²⁺ ions is added to NH_3(aq).

Use the data in the table to predict the formula of the complex formed in the greatest amount when a solution containing equal concentrations of both Hg²⁺ and Fe³⁺ ions is added to Cl^-_(aq).

Use the data in the table to predict the formula of the complex formed in the greatest amount when a solution containing equal concentrations of Cl^-, SCN^- and F^- ions is added to Fe³⁺_(aq).

The diagram below shows the structure of the multidentate ligand ethylenediaminetetraacetate, EDTA^4-.

Write an equation for the equilibrium that is established when hydrated chromium(III) ions, [Cr(H₂O)₆]³⁺, react with EDTA^4- ions to form the complex ion, [Cr(EDTA)]^-.

Name the type of reaction occuring in part a).

Write an expression for the stability constant, K_stab, of [Cr(EDTA)]^- in this reaction.

State the units of K_stab.

The value of K_stab for this equilibrium is 2.51 × 10²³ mol^-1 dm³.

Suggest what information can be deduced from the value of K_stab.

Explain why the equilbrium position lies almost completely to the right to form the EDTA complex.

Iron(III) forms complexes in separate reactions with both SCN^- ions and Cl^- ions.

Equilibrium 1:  Fe³⁺_(aq) + SCN^-_(aq) ⇌ [FeSCN]²⁺_(aq) 

Equilibrium 2:    Fe³⁺_(aq) + 4Cl^-_(aq) ⇌ [FeCl₄]^-_(aq)     

Write the expressions for the stability constants, K_stab, for these two equilibria.

Give the units of K_stab for both equilibria.

An equilibrium can be set up between these two complexes as shown in equilibrium 3.

Equilibrium 3:   [FeCl₄]^-_(aq) + SCN^-_(aq) ⇌ [FeSCN]²⁺_(aq) + 4Cl^-_(aq)

Write an expression for K_eq(3) in terms of K_stab(1) and K_stab(2).

The values for these stability constants are:

K_stab(1) = 140 mol^-1 dm³

K_stab(2) = 0.800 mol^-4 dm¹²

Calculate the value of K_eq(3) and state its units.

Give your answer to 3 significant figures.