COLOURS OF COMPLEX IONS

Question 1

Colour of precipitate formed from Cu2+ and 2OH-

Answer 1

Light blue

Question 2

Colour of precipitate formed from Fe2+ and 2OH-

Answer 2

Green, which oxidises to Fe(OH)3

Question 3

Colour of Fe(OH)3

Answer 3

Rust

Question 4

Colour of precipitate formed from Fe3+ and 3OH-

Answer 4

Rust coloured

Question 5

Colour of precipitate formed from Mn2+ and 2OH-

Answer 5

Pale pink which oxidises to Mn2O3

Question 6

Colour of Mn2O3

Answer 6

Brown

Question 7

Colour of precipitate formed from Cr3+ and 3OH-

Answer 7

Dark green

Question 8

How to identify CO3 2-

Answer 8

Add dilute acid, bubbling occurs and the gas given off turns limewater milky

Question 9

How to identify Cl-

Answer 9

Dissolve suspected chloride and add aqueous silver nitrate. White precipitate forms which is dissolved by dilute ammonia

Question 10

What ion is formed by AgCl and ammonia

Answer 10

[Ag(NH3)2]+

Question 11

How to identify SO4 2-

Answer 11

Dissolve sulfate and add barium nitrate. A white precipitate forms which is insoluble in dilute nitric acid

Question 12

How to identify NH4+

Answer 12

Warm ammonium compound with dilute aqueous NaOH. Will turn red litmus paper blue as it is alkaline

Question 13

How to identify Cu2+

Answer 13

Dissolve and add dilute aqueous ammonia. Light blue precipitate forms which turns deep blue when excess ammonia added

Question 14

How to identify Fe2+

Answer 14

Dissolve and add NaOH, green precipitate

Question 15

How to identify Fe3+

Answer 15

Dissolve and add NaOH, rust colour precipitate forms

Question 16

How to identify Mn2+

Answer 16

Dissolve and add NaOH, pale pink precipitate forms

Question 17

How to identify Cr3+

Answer 17

Dissolve and add NaOH, green precipitate forms which dissolves when excess NaOH is added
Cr compound