Transition Metals

Question 1

Give 2 examples of bidentate ligands.

Answer 1

1,2-diaminoethane and ethandioate.

Question 2

Give an example of a multidentate ligand.

Answer 2

EDTA4-

Question 3

Give the colour of Co (II) ions in an aqueous solution.

Answer 3

Pink solution.

Question 4

Describe the appearance of Cu (II) ions in an aqueous solution.

Answer 4

Blue solution.

Question 5

Describe the appearance of Cr (III) ions in an aqueous solution.

Answer 5

Ruby solution.

Question 6

Describe the appearance of Fe (III) ions in an aqueous solution.

Answer 6

Violet solution, although appears brown as [Fe(H₂O)₆]³⁺ is hydrolysed to [Fe(H₂O)₅(OH)]²⁺.

Question 7

Describe the appearance of Vanadium (III) ions in an aqueous solution.

Answer 7

Blue solution.

Question 8

Describe the appearance of Aluminium (III) ions in an aqueous solution.

Answer 8

Colourless solution.

Question 9

Which 3 metal ions can undergo complete ligand substitution in concentrated ammonia? Give the complexes and the appearances of these.

Answer 9

Co (II) [Co(NH₃)₆]²⁺ - Straw coloured solution;
Co (III) [Co(NH₃)₆]³⁺ - Dark brown solution;
Cr (III) [Cr(NH₃)₆]³⁺ - Purple solution.

Question 10

Which metal ion undergoes partial ligand substitution with NONE EXCESS ammonia (to form an AQUEOUS SOLUTION)? Give the equation and appearance of the metal reactant and product.

Answer 10

[Cu(H₂O)₆]²⁺ + 4NH₃ → [Cu(H₂O)₂(OH)₄]²⁻ + 4NH₄⁺

Original appearance: Blue solution.
Final appearance: Deep blue solution.

Question 11

Which two metal ions make complexes with chloride? Give the complex and the appearance.

Answer 11

Co (II) ions: [CoCl₄]²⁻, blue solution.

Cu (II) ions: [CuCl₄]²⁻, yellow-green solution.

Question 12

Which three metal(II) ions make compounds with carbonate? Give the compounds and their appearances.

Answer 12

Co (II) ions: CoCO₃, pink precipitate.
Cu (II) ions: CuCO₃, green-blue precipitate.
Fe (II) ions: FeCO₃, green precipitate.

Question 13

Give the general reaction of hexaaqua metal(II) complexes with carbonate ions.

Answer 13

[M(H₂O)₆]²⁺(aq) + CO₃²⁻(aq) → MCO₃(s) + 6H₂O(l)

Question 14

Give the general reaction of hexaaqua metal(III) complexes with carbonate ions.

Answer 14

2[M(H₂O)₆]³⁺(aq) + 3CO₃²⁻(aq) → 2M(H₂O)₃(OH)₃ + 3CO₂(g) + 3H₂O(l)

Question 15

What is the source of our carbonate ions?

Answer 15

Na₂CO₃

Question 16

Give the reaction of hexaaqua metal(II) complexes with dilute ammonia (to form a SOLID).

Answer 16

[M(H₂O)₆]²⁺(aq) + 2NH₃(aq) → M(H₂O)₄(OH)₂ + 2NH₄⁺(aq)

Question 17

Give the reaction of hexaaqua metal(III) complexes with dilute ammonia.

Answer 17

[M(H₂O)₆]³⁺(aq) + 3NH₃(aq) → M(H₂O)₃(OH)₃ + 3NH₄⁺(aq)

Question 18

Give the equation for complete ligand substitution with excess ammonia, and name the three ions that this works with.

Answer 18

[M(H₂O)₆]ⁿ⁺ + 6NH₃ → [M(NH₃)₆]ⁿ⁺ + 6H₂O.

Co(II), Co(III), Cr(III)