Question

Q3

The EDTA4- ligand is multidentate with the structural formula shown below. Four of the atoms which can bond to a metal ion are marked with crosses.

Questions:

a) using crosses, indicate where two other atoms could bond in metal ions when EDTA4- forms complexes( 2 marks)

b) explain the term multidentate ligand? (2 marks)

c) The EDTA4- ion reacts with metal(II) ions according to the equation shown below

(M(H2O)6)2+ + EDTA4- —> M(EDTA)2- + 6H2O

in a titration, using a suitable indicator, the following measurements were made:

A solution containing 0.0624 g of hydrated copper(II) sulphate reacted exactly with 25.00 cm3 of 0.0100 M EDTA 4- solution.

using the information, calculate the value of n in the formula of the hydrated copper(II) sulphate, CuSO4 . nH2O (6 marks)

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Answer 1

(a)

(b)

Multidentate are Ligands with more than one bonded atom.

(c)

Moles of EDTA$^{4-}$ used

$=\frac{25}{1000}×0.01=0.00025$

Reacting ratio $=1:1$

$\implies$ moles of hydrated copper (ii) Sulphate

$=0.00025$

$0.00025$ moles $\equiv0.0624g$

$1\>mole=\frac{0.0624}{0.0025}=249.6$

Molar mass of Anhydrous copper (ii) Sulphate

$=159.6$

Mass of water $=249.6-159.6$

$=90$

Molar mass of water$=18g$

$n=\frac{90}{18}=5$