Transition Metal Colours

Question 1

General change for chromium

Answer 1

Violet sol to green ppt to green sol to purple sol

Question 2

What is the general trend for Fe2+

Answer 2

Green sol to green ppt (oxidises to brown ppt)

Question 3

General solution for Fe3+

Answer 3

Yellow sol to brown ppt

Question 4

General trend for Cu2+

Answer 4

Blue sol to blue ppt to deep blue sol to yellow sol

Question 5

General trend for Co2+

Answer 5

Pink sol to blue ppt to brown sol (oxidises to yellow in air) to blue sol

Question 6

Formula and colour of Cr3+ and a few drops of NaOH/NH3 and change in colour from ion

Answer 6

[Cr(H2O)3(OH)3]

Green ppt

Violet to green

Question 7

Formula and colour of Cr3+ and excess NaOH and change in colour from ion

Answer 7

[Cr(OH)6]3-

Green solution

Violet to green

Question 8

Formula and colour of Cr3+ and excess NH3 and change in colour from ion

Answer 8

[Cr(NH3)4]3+

Purple sol

Violet to purple

Question 9

Formula and colour of Fe2+ and a few drops of NaOH/NH3 and change in colour from ion

Answer 9

[Fe(H2O)4(OH)2]

Green ppt

Green to green

Question 10

Formula and colour of Fe3+ and a few drops of NaOH/NH3 and change in colour from ion

Answer 10

[Fe(H2O)3(OH)3]

Brown ppt

Yellow to brown

Question 11

Formula and colour of Cu2+ and a few drops of NaOH/NH3 and change in colour from ion

Answer 11

[Cu(H2O)4(OH)2]