Solubility of Metal Sulfides | Soluble or Insoluble?

Solubility of Metal Sulfides in Water| Soluble and Insoluble?

There are soluble metal sulfides in the water and insoluble metal sulfides. Most of the insoluble metal sulfides have colours. In this tutorial, you are going to learn which metal sulfides are insolube in water and what are the colours of them if they have colours.

inorganic chemistry, Solubility of inorganic compounds

All Metal sulfides dissolve in dilute acids and produce hydrogen sulfide gas and metal salt.

CuS + HCl → CuCl2 + H2S

As an example, copper sulfide (CuS) is a black precipitate and dissolve in dilute HCl acid and form blue color CuCl2 solution.

Colours of metal sulfides are important in identifying compounds in inorganic chemistry.

S block metal sulfides - Alkali metals and alkaline earth metals

All alkali metals sulfide and alkaline earth metals sulfides are soluble in water and form colourless aqueous solutions. But due to instability of sulfide ion, sulfide ion can hydrolysis and emit hydrogen sulfide gas by giving strong aqueous solution.

Sodium sulfide

Sodium sulfide is soluble in water. But it hydrolysis to sodium hydroxide and hydrogen sulfide gas by forming a strong aqueous solution.

Na2S + H2O → 2NaOH + H2S

P block metal sulfides solubility and colors

Some p block metals form soluble sulfide compounds and some form insoluble metal sulfides.

Aluminium sulfide - Al2S3

Aluminium sulfide dissolve in water and hydrolysis like sodium sulfide and emits hydrogen sulfide gas. Also a white precipitate, aluminium hydroxide ( Al(OH)3 ) is given.

Tin(II) sulfide - SnS

This is the sulfide of tin's +2 oxidation state. Tin(II) sulfide is insoluble in water and form a yellow brown or dark brown precipitate in water.

Tin(IV) sulfide - SnS2

Tin(IV) sulfide is insoluble in water and form a yellow precipitate in water.

Lead sulfide - PbS

Lead sulfide is insoluble in water and form a black precipitate in water.

Antimony sulfide - Sn2S3

Antimony sulfide is insoluble in water and form a orange color precipitate in water.

Bismuth sulfide - Bi2S3

Bismuth sulfide is insoluble in water and form a orange brown precipitate in water.

3d metal sulfides

3d metal sulfides are insoluble in water and show colors. 3d metal sulfides are MnS, FeS, Fe2S3, CoS, NiS, CuS and ZnS.

In qualitative analysis, sulfide precipitating is done in two ways due to solubility of different metal sulfide's are different.

  1. Acidic medium precipitating
  2. Basic medium precipitate

Insoluble metal sulfides with colors

These insoluble metal sulfides have very low Ksp values and solubility values.

Metal sulfide Chemical Formula Colour
Mercuric sulfide HgS Black
Antimony trisulfide Sb2S3 red-orange
Cadmium sulfide CdS yellow
Ferrous sulfide / Iron(II) sulfide FeS Black
Stannous sulfide / Tin(II) sulfide SnS Yellow brown or dark brown
Tin(IV) sulfide SnS2 yellow
Copper sulfide CuS Black
Copper sulfide CuS Black
Zinc sulfide ZnS White
Manganese sulfide MnS Pink
Nickel sulfide NiS Black
Cobalt sulfide CoS Black
Lead sulfide PbS Black
Bismuth sulfide Bi2S3 Brown

Questions asked by students

Copper (II) sulfide soluble or insoluble?

Copper(II) sulfide is insoluble in water and forms a black precipitate. Also copper(I) sulfide is insoluble in water.

CoS soluble or insoluble

Solubility of CoS is 0.00038 g/100 mL of water at 180C. So CoS is insoluble in water but soluble in dilute acids.

sodium sulfide soluble or insoluble?

All alkali metal sulfides are soluble in water. But sodium sulfide is not stable in water and it is hydrolyzed to sodium hydroxide by giving strong alkaline solution.

How about the Ksp values of soluble sulfides and insoluble sulfides

Ksp means solubility product. When Ksp value is low, it indicates that compound has a lower solubility in water. Lets take several metal sulfides to learn this.

  • Ksp of CuS : 1 * 10-36 mol2 dm-6
  • Ksp of ZnS : 1 * 10-23 mol2 dm-6

You see these metal sulfide's Ksp values are very low and they form precipitates in the water

Can sodium sulfide is used to recover hydrogen sulfide in petroleum industry

First of all, I should say, this is an idea. After hydrogen sulfide and other effluent gases are separated in the refining process, it should be sent to aqueous concentrated NaOH solution to produce sodium sulfide. Then other gases are removed. Produced sodium sulfide is sent into another place and heat the solution. Then sodium sulfide will hydrolysis will emit hydrogen sulfide gas.

is CoS soluble in water?

You can see, a black color solid is deposited as CoS precipitate in the water. Therefore, CoS is insolble in water.

Related tutorials for sulfide ion

Testing sulfide ion Testing S2O32- ions Testing SO42- ions 3d metals colours, oxidation numbers, compounds