Topic 14 Colors

Question 1

Hydrated Copper2+ reactions with:
Starting
Conc Cl
Few Drops OH-/NH3
Few Drops OH-/NH3 and air
Excess NH3
Excess NH3 and air

Answer 1

Blue

Conc Cl - GREEN (CuCl4)

Few Drops OH-/NH3 - Blue ppt Cu(OH)2(H20)4

Few Drops OH-/NH3 and air - nothing

Excess NH3 - Deep blue solution ( Cu(NH3)4H20(2)

Excess NH3 and air - nothing

Question 2

Hydrated Cobalt2+ reactions with:
Starting
Conc Cl
Few Drops OH-/NH3
Few Drops OH-/NH3 and air
Excess NH3
Excess NH3 and air

Answer 2

Pale Pink

Conc Cl - Blue solution (CoCl4)

Few Drops OH-/NH3 - Blue ppt (Co(OH)2(H20)4

Few Drops OH-/NH3 and air - Brown ppt
(Co(OH)3(H20)3)

Excess NH3 - Yellow solution
(Co(NH3)6)2+

Excess NH3 and air - Brown solution
(Co(NH3)6)3+

Question 3

Hydrated Fe2+ reactions with:
Starting
Conc Cl
Few Drops OH-/NH3
Few Drops OH-/NH3 and air
Excess NH3
Excess NH3 and air

Answer 3

Green

Conc Cl - Nothing

Few Drops OH-/NH3 - Green ppt
Fe(OH)2(H20)4

Few Drops OH-/NH3 and air - Brown ppt
Fe(OH)3(H20)3

Excess NH3 - Nothing

Excess NH3 and air - Nothing

Question 4

Hydrated Fe3+ reactions with:
Starting
Conc Cl
Few Drops OH-/NH3
Few Drops OH-/NH3 and air
Excess NH3
Excess NH3 and air

Answer 4

Yellow

Conc Cl - Nothing

Few Drops OH-/NH3 - Brown ppt
Fe(OH)3(H20)3

Few Drops OH-/NH3 and air - Nothing

Excess NH3 - Nothing

Excess NH3 and air - Nothing

Question 5

Hydrated Cr3+ reactions with:
Starting
Conc Cl
Few Drops OH-/NH3
Few Drops OH-/NH3 and air
Excess NH3
Excess NH3 and air

Answer 5

Violet

Conc Cl - Nothing

Few Drops OH-/NH3 - Green ppt
Cr(OH)3(H20)3

Few Drops OH-/NH3 and air - Nothing

Excess NH3 - Violet
Cr(NH3)6

Excess NH3 and air - nothing

Question 6

Cr(OH)3(H20)3 to Dichromate steps
Dichromate back to green solution of what?

Answer 6

Cr(OH)3(H20)3 + XS OH to form Cr(OH6) yellow solution
Add H202 to form chromate (Yellow)
Add acid to form dichromate
Dichromate + Zinc and HCl to form Cr (H20)6