Precipitate and Ion Colours

Question 1

[Cu(H2O)6]2+

Answer 1

Blue solution

Question 2

Cu(OH)2

Answer 2

Pale blue gelatinous precipitate.

Question 3

Is Cu(OH)2 soluble?

Answer 3

• Soluble on addition of further aqueous ammonia ions

- Insoluble on addition of further aqueous hydroxide ions

Question 4

[Cu(NH3)4(H2O)2]2+

Answer 4

Deep blue solution

Question 5

[CuCl4]2-

Answer 5

Yellow solution

Question 6

Mix of [CuCl4]2- and [Cu(H2O)6]2+

Answer 6

Green solution (commonly seen during experiments as it is nearly impossible to isolate the [CuCl4]2-)

Question 7

[Cr(H2O)6]3+

Answer 7

Purple solution

Question 8

Cr(OH)3

Answer 8

Grey-green precipitate

Question 9

Is Cr(OH)3 soluble?

Answer 9

It is soluble on addition of both addition of aqueous ammonia ions and aqueous hydroxide ions

Question 10

[Cr(OH)6]3-

Answer 10

Dark green solution

Question 11

[Cr(NH3)6]3+

Answer 11

Purple solution

Question 12

[Fe(H2O)6]2+

Answer 12

Pale green solution

Question 13

Fe(OH)2

Answer 13

Green gelatinous precipitate

Question 14

Is Fe(OH)2 soluble?

Answer 14

It is insoluble on further addition of aqueous hydroxide ions, but over time the Fe2+ is oxidised

Question 15

Fe(OH)3

Answer 15

Orange-brown precipitate

Question 16

[Fe(H2O)6]3+

Answer 16

Yellow solution

Question 17

Is Fe(OH)3 soluble?

Answer 17

It is insoluble on further addition of aqueous hydroxide ions

Question 18

[Mn(H2O)6]2+

Answer 18

Very pale pink solution

Question 19

Mn(OH)2

Answer 19

Brown precipitate

Question 20

Is Mn(OH)2 soluble?

Answer 20

It is insoluble on further addition of aqueous hydroxide ions