Transition metals

Question 1

Dilute aqueous ammonia is added to an aqueous solution of copper(II) sulfate until the aqueous ammonia is in excess.
What would you see and what is the equation?

Answer 1

Pale blue precipitate to a deep blue solution.
[Cu(H2O)6]2+ + 4NH3 —> [Cu(NH3)4(H2O)2]2+ + 4H2O

Question 2

Dilute aqueous ammonia is added to an aqueous solution of copper(II) sulfate. What would you see and what is the equation?

Answer 2

[Cu(H2O)6]2+ +2NH3 —> [Cu(H2O)4(OH)2] + 2NH4+

pale blue solution to blue precipitate

Question 3

Describe the reaction of aqueous copper(II) ions with aqueous sodium hydroxide solution and the observations you would expect.

Answer 3

Pale blue precipitate to blue precipitate
[Cu(H2O)6]2+ +2OH- —> [Cu(H2O)4(OH)2] + 2H2O

Question 4

Describe the reaction of aqueous copper(II) ions with concentrated hydrochloric acid and the observations you would expect.

Answer 4

Pale blue precipitate forms a yellow solution
[Cu(H2O)6]2+ 4Cl- —> [CuCl4]2- + 6H2O

Question 5

The colour of VO2 +

Answer 5

yellow

Question 6

The colour of VO 2+

Answer 6

blue

Question 7

The colour of V 3+

Answer 7

green

Question 8

The colour of V 2+

Answer 8

purple

Question 9

State the initial and final colours you would see as chlorine bubbles through aqueous vanadium(II) chloride, VCl2(aq).

Answer 9

Puple to yellow solution

Question 10

What is the ionic equation for the reaction of solid chromium(III) hydroxide with dilute hydrochloric acid and the observations you would expect to see.

Answer 10

Green solid to green solution
Cr(OH)3 + 3H2O + 3H+ —> [Cr(H2O)6]3+

Question 11

The ionic equation for the reaction of solid chromium(III) hydroxide with dilute sodium hydroxide solution and the observations you would expect to see.

Answer 11

Green solid to green solution.
Cr(OH)3 + 3OH- —> [Cr(OH)6]3-

Question 12

Deduce the oxidation half-equation and normal equation for the oxidation of [Cr(OH)6]3− to chromate(VI) ions (in alkaline conditions) and the observations you would expect to see.

Answer 12

Green solution to yellow solution
[Cr(OH)6]3- + 2OH- —> CrO4 2- + 4H2O + 3e-
[Cr(OH)6]3- + 3H2O2 —> 2CrO4 2- + 8H2O + 2OH-

Question 13

The equation for the reaction when chromate(VI) ions are acidified to dichromate(VI) ions and the observations you would expect.

Answer 13

Yellow solution to orange solution
2CrO4 2- + 2H+ —> Cr2O7 2- + H2O

Question 14

The colour change that occurs when dichromate (VI) to Cr 3+

Answer 14

Orange to green

Question 15

The colour change that occurs when Cr 3+ is reduced to Cr 2+

Answer 15

green to blue

Question 16

The equation for the reaction between cobalt (II) solution and sodium hydroxide and the observations you would expect.

Answer 16

Pink solution to blue precipitate
[Co(H2O)6]2+ + 2OH- —> [Co(H2O)4(OH)2] + 2H2O

Question 17

The equation for the reaction between cobalt (II) solution and aqueous ammonia and the observations you would expect.

Answer 17

Pink solution to blue precipitate
[Co(H2O)6]2+ + 2NH3 —> [Co(H2O)4(OH)2] + 2NH4+

Question 18

The equation for the reaction between cobalt (II) solution and excess aqueous ammonia and the observations you would expect.

Answer 18

Pink solution to blue precipitate to brown solution
[Co(H2O)6]2+ + 2NH3 —> [Co(H2O)4(OH)2] + 2NH4+
[Co(H2O)4(OH)2] + 6NH3 —> [Co(NH3)6]2+ + 4H2O + 2OH-

Question 19

The equation for the reaction between cobalt (II) solution and concentrated HCl and the observations you would expect.

Answer 19

Pink solution to blue solution
[Co(H2O)6]2+ + 4Cl- —> [CoCl4]2- + 6H2O

Question 20

The equation for the reaction between iron (II) solution and aqueous sodium hydroxide and the observations you would expect.

Answer 20

Pale green solution to green precipitate
[Fe(H2O)6]2+ + 2OH- —> [Fe(H2O)4(OH)2] + 2H2O

Question 21

The equation for the reaction between iron (II) solution and aqueous ammonia and the observations you would expect.

Answer 21

Pale green solution to green precipitate
[Fe(H2O)6]2+ + 2NH3 —> [Fe(H2O)4(OH)2] + 2NH4+

Question 22

The equation for the reaction between iron (III) solution and aqueous sodium hydroxide and the observations you would expect.

Answer 22

Yellow brown solution to brown precipitate
[Fe(H2O)6]3+ + 3OH- —> [Fe(H2O)3(OH)3] + 3H2O

Question 23

The equation for the reaction between iron (III) solution and aqueous ammonia and the observations you would expect.

Answer 23

Yellow brown solution to brown precipitate
[Fe(H2O)6]3+ + 3NH3 —> [Fe(H2O)3(OH)3] + 3NH4+

Question 24

The equation for the reaction of chromium(III) solution with dilute sodium hydroxide solution and the observations you would expect to see.

Answer 24

Green solution to green precipitate
[Cr(H2O)6]3+ + 3OH- —> [Cr(H2O)3(OH)3] + 3H2O

Question 25

The equation for the reaction of chromium(III) solution with aqueous ammonia and the observations you would expect to see.

Answer 25

Green solution to green precipitate
[Cr(H2O)6]3+ + 3NH3 —> [Cr(H2O)3(OH)3] + 3NH4+