EDTA⁴⁻, is a polydentate ligand.

1. (a)(i)Explain what is meant by the term polydentate ligand.[2]
2. (a)(ii)When a solution containing EDTA⁴⁻ is added to a solution containing [Cd(H₂O)₆]²⁺ a new complex is formed, [CdEDTA]²⁻. equilibrium 1 [Cd(H₂O)₆]²⁺ + EDTA⁴⁻ ⇌ [CdEDTA]²⁻ + 6H₂O Circle, on the structure of EDTA⁴⁻, the six atoms that form bonds with the metal ion. EDTA⁴⁻ -O-CCH₂ CH₂C-O- NCH₂CH₂N -O-CCH₂ CH₂C-O-[1]
3. (a)(iii)Write an expression for the stability constant, Kstab1, for equilibrium 1, and state its units. Kstab1 = units =[2]
4. (b)(i)Keq4 is the equilibrium constant for equilibrium 4. Write an expression for Keq4 in terms of Kstab2 and Kstab3. Keq4 =[1]
5. (b)(ii)Calculate the value of the standard Gibbs free energy change, ∆G°, for equilibrium 4 at 298 K. ∆G° = kJ mol⁻¹ [2][2]
6. (b)(iii)State how the value of ∆G° changes as the temperature increases. Explain your answer.[1]

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