transition elements colours

Question 1

Fe 2+

Answer 1

pale green

Question 2

Fe 3+

Answer 2

yellow

Question 3

Fe(OH)2

Answer 3

green

Question 4

[Cu(H2O)6] 2+

Answer 4

pale blue

Question 5

Cu(OH)2(s)

Answer 5

pale blue ppt

Question 6

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

Answer 6

dark blue

Question 7

CuCl4 2–

Answer 7

yellow

Question 8

Cu+

Answer 8

white ppt (CuI) and brown I2

Question 9

Cu2+ / Cu

Answer 9

Disproportionation of Cu+
brown solid (Cu) and
blue solution (CuSO4)

Question 10

CoCl4 2–

Answer 10

blue

Question 11

[Cr(H2O)6] 3+

Answer 11

pale purple
(heat green)

Due to impurities, it is common for Cr(III) to appear green in solution

Question 12

Cr(OH)3(s)

Answer 12

NH3 dropwise to Cr 3+(aq)

dark green precipitate

Question 13

[Cr(NH3)6] 3+

Answer 13

excess NH3 to Cr 2+(aq)

purple

Question 14

[Cr(OH)6] 3–

Answer 14

excess OH– to Cr(OH)3
(s) dark green

Question 15

Cr2O7 2–

Answer 15

from K2Cr2O7(s) in 0.1mol dm-3 H2SO4

orange

Question 16

CrO4 2–

Answer 16

oxidation of Cr3+ with hot alkaline H2O2
yellow

Question 17

[Mn(H2O)6] 2+

Answer 17

from MnSO4.4H2O(s)
pale pink

Question 18

Mn(OH)2(s)

Answer 18

NaOH dropwise to Mn2+(aq)
pale brown precipitate

Question 19

[Fe(H2O)6] 2+

Answer 19

from FeSO4.7H2O(s)
pale green

Question 20

Fe(OH)2(s)

Answer 20

NaOH dropwise to Fe2+(aq)
dark green precipitate

Question 21

[Fe(H2O)6] 3+

Answer 21

from FeCl3.6H2O(s)
yellow