Transition Metals Colour Changes

Question 1

[Cu(H2O6)]^2+

from CuSO4.H2O (s)

Answer 1

Pale Blue

Question 2

Fe3+ (aq) + 3OH- (aq) –> Fe(OH)3 (s)

Answer 2

yellow —> orange brown precipitate

Question 3

Fe2+ (aq) + 2OH- —> Fe(OH)2 (s)

Answer 3

pale green –> dark green precipitate

Question 4

Cu2+ (aq) 2OH- —> Cu(OH)2(s)

Answer 4

pale blue –> pale blue precipitate

Question 5

Mn2+ (aq) + 2OH- —> Mn(OH)2(s)

Answer 5

pale pink —> pale brown precipitate

Question 6

Cr3+ (aq) + 3OH- (aq) —> Cr(OH)3(s)

Answer 6

violet / pale purple —> dark green precipitate

Question 7

Cr(OH)3(s) + 3OH - (aq) —> [Cr(OH)6]3- (aq)

Answer 7

dark green precipitate —> dark green solution

Question 8

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

excess NH3 to Cu2+ (aq)

Answer 8

dark blue

Question 9

CuCl4 2-

excess HCL to Cu2+ (aq)

Answer 9

yellow

Question 10

Cu+

reduction of Cu2+ with I-

Answer 10

White precipitate (Cu) and brown I2

Question 11

Cu2+ / Cu

Disproportionation of Cu+

Answer 11

brown solid (Cu) and blue solution (CuSO4)

Question 12

CoCl4 2-

from CoCl2.6H2O(s) + water and excess HCl

Answer 12

blue

Question 13

[Cr(H2O)6]3+

from KCr(SO4)2.12H2O(s)

Answer 13

pale purple (heat = green)
Due to impurities the Cr(III) can appear green in solution.

Question 14

Cr(OH)3

NH3 dropwise to Cr3+ (aq)

Answer 14

dark green precipitate