Complex ion solution colours

Question 1

Cu2+ in aqueous solution

Answer 1

BLUE
Cu2+ (aq) or [Cu(H2O)6]^2+ (aq)

Question 2

Fe2+ in aqueous solution

Answer 2

PALE GREEN
Fe2+ (aq) or [Fe(H20)6]^2+ (aq)

Question 3

Fe3+ in aqueous solution

Answer 3

YELLOW
Fe3+ (aq) or [Fe(H20)6]^3+ (aq)

Question 4

Mn2+ in aqueous solution

Answer 4

PALE PINK
Mn2+(aq) or [Mn(H20)6]^2+ (aq)

Question 5

Cr3+ in aqueous solution

Answer 5

GREEN
Cr3+(aq) or [Cr(H20)6]^3+ (aq)

Question 6

Adding some OH- (aq) or NH3 (aq) to aqueous solution of Cu2+

Answer 6

PALE BLUE PRECIPITATE
Cu(OH)2(H2O)4 (s)

Question 7

Adding some OH- (aq) or NH3 (aq) to aqueous solution of Fe2+

Answer 7

DIRTY GREEN PRECIPITATE
Fe(OH)2(H2O)4 (s)

Question 8

Adding some OH- (aq) or NH3 (aq) to aqueous solution of Fe3+

Answer 8

ORANGE PRECIPITATE
Fe(OH)3(H2O)3 (s)

Question 9

Adding some OH- (aq) or NH3 (aq) to aqueous solution of Mn2+

Answer 9

PINK PRECIPITATE
Mn(OH)2(H2O)4 (s)

Question 10

Adding some OH- (aq) or NH3 (aq) to aqueous solution of Cr3+

Answer 10

GREEN-GREY PRECIPITATE
Cr(OH)3(H2O)3 (s)

Question 11

Adding excess OH- to the precipitate of Cu2+, Fe2+, Fe3+, Mn2+

Answer 11

NO CHANGE
(insoluble in excess NaOH )

Question 12

Adding excess OH- to the precipitate of Cr3+

Answer 12

Cr(OH)6 ^3- (aq)
DARK GREEN SOLUTION

Question 13

Adding excess NH3(aq) to the precipitate of Fe2+, Fe3+, Mn2+

Answer 13

NO CHANGE
Insoluble in excess NH3

Question 14

Adding excess NH3(aq) to the precipitate of Cu2+

Answer 14

DARK BLUE SOLUTION (part ligand substitution)
[Cu(NH3)4(H2O)2]^2+ (aq)

Question 15

Adding excess NH3(aq) to the precipitate of Cr3+

Answer 15

PURPLE SOLUTION
Cr(NH3)6^3+ (aq)