Transition metals

Question 1

What colour is [Cu(H₂O)₆]²⁺ ?

from CuSO4.5H2O(s)

Answer 1

pale blue solution

Question 2

What colour is [Mn(H₂O)₆]²⁺ ?

from MnSO4.4H2O(s)

Answer 2

pale pink solution

Question 3

What colour is [Fe(H₂O)₆]²⁺ ?

from FeSO4.7H2O(s)

Answer 3

pale green solution

Question 4

What colour is [Cr(H₂O)₆]³⁺ ?

from KCr(SO4)2.12H2O(s)

Answer 4

pale green
(pale purple, due due to impurities it is common for it to appear green in solution)

Question 5

What colour is [Cr(OH)₆]³⁻ ?

excess OH– to Cr(OH)3 (s)

Answer 5

dark green solution

Question 6

What colour is [Fe(H₂O)₆]³⁺ ?

from FeCl3.6H2O(s)

Answer 6

yellow solution

Question 7

What colour is [CuCl₄]²⁻ ?

excess HCl to Cu2+(aq)

Answer 7

yellow solution

Question 8

What colour is [CrO₄]⁻ ?

oxidation of Cr3+ with
hot alkaline H2O2

Answer 8

yellow solution

Question 9

What colour is [Cu(H₂O)₂(NH₃)₄]²⁺ ?

excess NH3 to Cu2+(aq)

Answer 9

deep blue

Question 10

what colour is [Cu(OH)₂(H₂O)₄] ?

NH3 dropwise to Cu2+(aq)

Answer 10

pale blue precipitate

Question 11

What colour is [Fe(OH)₂(H₂O)₄] ?

NaOH dropwise to Fe2+(aq)

Answer 11

dark green precipitate

Question 12

What colour is [Cr(OH)₃(H₂O)₃] ?

NH3 dropwise to Cr 3+(aq)

Answer 12

dark green

Question 13

What colour is [Fe(OH)₃(H₂O)₃] ?

NaOH dropwise to Fe3+(aq)

Answer 13

orange/brown precipitate

Question 14

What colour is [Mn(OH)₂(H₂O)₄] ?

NaOH dropwise to Mn2+(aq)

Answer 14

pale brown/pink precipitate

Question 15

What colour is [Cr(NH₃)₆]³⁺ ?

excess NH3 to Cr 2+(aq)

Answer 15

purple solution

Question 16

What colour is [MnO₄]⁻ ?

Answer 16

purple solution

Question 17

What colour is Mn2+?

Answer 17

pale pink solution

Question 18

What colour is Cu+ ?

reduction of Cu2+ with I–

Answer 18

white precipitate and brown I2

Question 19

What colour is Cu2+/Cu?’

Disproportionation of Cu+

Answer 19

brown solid (Cu) and
blue solution (CuSO4)

Question 20

What colour is CoCl4 2-?

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

Answer 20

Blue

Question 21

What colour is Cr2O7 2-?

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

Answer 21

orange

Question 22

Oxidation of Fe2+ to Fe3+
Colour change and reactants ?

Answer 22

Green to Yellow
H+ and MnO4-

Question 23

Reduction of Fe3+ to Fe2+
Colour change and reactants?

Answer 23

Yellow to green
I-

Question 24

Oxidation of Cr3+ to CrO42-
Colour change and reactants?

Answer 24

Green to yellow
H2O2/OH-

Question 25

Reduction of Cr2O7 2- to Cr3+ Colour change and reactants

Answer 25

Orange to green Zn/H+

Question 26

Reduction of Cu2+ to Cu+ Colour change and reactants

Answer 26

Blue to colourless solution (white precipitate dissolves) I-