RQP 11: Testing aqeous transition metal ions

Question 1

What are the NH3 and OH- ions acting as when they react with transition metal aqua ions

Answer 1

Bronsted-Lowry bases as the accept a proton.

Question 2

When are the hydroxide precipitates of transition metal ions formed

Answer 2

In deprotonation acid-base reactions with OH- and NH3

Question 3

What colour is the copper (II) hydroxide [Cu(OH)2(H20)4] precipitate

Answer 3

Blue

Question 4

What colour is the iron (II) hydroxide [Fe(OH)2(H20)4] precipitate

Answer 4

Green

Question 5

What colour is the iron (III) hydroxide [Fe(OH)3(H20)3] precipitate

Answer 5

Brown

Question 6

What colour is the aluminium (III) hydroxide [Al(OH)3(H20)3] precipitate

Answer 6

White

Question 7

Which transition metal hydroxide precipitate redissolves in excess NH3 and what colour of solution is formed

Answer 7

Cu (II) and a deep blue solution is formed

Question 8

Which transition metal hydroxide precipitate redissolves in excess OH- and what colour solution is formed

Answer 8

Aluminium (III) hydroxide and a colourless solution is formed

Question 9

What species is formed when aluminium hydroxide reacts with excess OH-

Answer 9

[Al(OH)4]-

Question 10

What species is formed when copper hydroxide reacts with excess NH3

Answer 10

[Cu(NH3)4(H20)2]2+

Question 11

What do transition metal aqua ions form when they react with carbonate ions

Answer 11

• 2+ ions form a metal carbonate
• 3+ ions form the metal hydroxide ion

Question 12

What forms when the cu(II) aqua ions reacts with carbonate

Answer 12

Blue-green precipitate of copper carbonate

Question 13

What forms when Fe (II) aqua ions react with carbonate

Answer 13

Green precipitate of iron carbonate

Question 14

Why do transition metal 2+ ions react with carbonate solutions to form a metal carbonate but transition metal 3+ ions do not

Answer 14

3+ ions have a greater polarising power due to their greater charge density