List of Precipitates Compounds Colours

A solid substance that has been separated from a liquid in a chemical process is called a precipitate. That process is defined as precipitating. Precipitates can be coloured or not. Forming precipitates and colours of precipitates are used to identify anions, cations, and compounds.

e.g:

• CaCO₃ (solid phase) does not dissolved in water (liquid phase).
• BaSO₄ (solid phase) does not dissolved in water (liquid phase).

Therefore, CaCO₃ and BaSO₄ are called as precipitates and both of them are white colour precipitates.

A precipitate in the aqueous solution

In this tutorial we cover following lessons.

1. Precipitates and solutions
2. Precipitates of s block, p block, d block elements
3. Precipitates categorized as anions and cations : This section is bit different. Some anions form solutions with some cations. But with some cation, they form precipitates. As an example chloride ion can be given. Chloride ion with sodium ion form sodium chloride which is highly soluble in water. But, with lead +2 ion, it forms lead chloride (PbCl₂) white precipitate. In this section, we learn that type of variations too.

What are the precipitates?

If there is a precipitate in the aqueous solution, we can see it easily. Because precipitate is in the solid phase and deposited at bottom of the solution after kept it sometime to settle down.

Why colours of precipitates are important?

Colours of precipitates help to identify compounds. We can decide which ions (cations or anions) are in the compound by comparing colours of different precipitates.

Example: Compare AgCl and AgBr precipitates. Ag⁺ ion is common in both compounds. But their colours are different due to different halide ions. AgCl is a white precipitate and AgBr is a light yellow precipitate.

Now we are going to list all precipitates according to the s block, p block and d block and colours.

Precipitates of s block

S block contains the alkali metals and alkali earth metals. Most of precipitates of alkali metals and alkali earth metals are white.

Precipitates of alkali metals

• Most of the alkali metals compounds are soluble in water. Lithium forms some insoluble compounds in water. LiF, Li₂CO₃, Li₂C₂O₄ are sparingly dissolve in water.
• Solubility of NaHCO₃ is also less than KHCO₃. Less solubilty of NaHCO₃ is very important factor in sodium carbonate manufacturing process by solvay process.

precipitates of alkaline earth metals

Alkaline earth metals forms both precipitates and solutions.

• All carbonates (CO₃^2-) of alkali earth metal ions are precipitates
  CaCO₃, MgCO₃, SrCO₃ are precipitates and they are white.
  
• SrSO₄, BaSO₄ are white colour precipitates.
• Be(OH)₂, Mg(OH)₂ are insoluble in water. Ca(OH)₂ is fairly soluble.
  Sr(OH)₂ and Ba(OH)₂ are readily soluble and they are strong alkalis.
• BeO, MgO are insoluble in water. When they are added to water, they are converted to their hydroxides. These hydroxides are insoluble in water. Beryllium hydroxide ( Be(OH)₂ ) is an amphoteric hydroxide compound.

Precipitates of 3d block metals

Most of 3d block metals precipitates show colours. Therefore we can use their precipitates colours to identify 3d metal ions. Below, we are listing precipitates of 3d metals with their colours according to the anion.

Precipitates list of 3d metals hydroxides

• Cr(OH)₃ - green
• Mn(OH)₂ - yellow white
• Fe(OH)₂ - green
• Fe(OH)₃ - brown
• Co(OH)₂ - pink
• Ni(OH)₂ - green
• Cu(OH)₂ - blue
• Zn(OH)₂ - white

Chromium hydroxide ( Cr(OH)₃ ) is dissolved when excess NaOH is added and give green colour solution. Cr(OH)₃ is an amphoteric compound.

Precipitates of sulfides of 3d metals, d block metals and p block metal cations

Most of the 3d metal sulfide are not soluble and they have different colours too.

• HgS_(s) - black
• Sb₂S_3(s) - orange
• CdS_(s) - yellow
• FeS_(s) - black
• SnS_(s) - yellow brown
• SnS_2(s) - yellow
• CuS_(s) - black
• NiS_(s) - black
• MnS_(s) - pink

Precipitates of anions

Carbonate, sulfate, sulphite, phosphate, sulfide, chloride, bromide, iodide and more anions form precipitates with some metal ions. Now we consider about those precipitate of anions and those precipitates colours.

Precipitates of carbonate ion, colours

Solubility of carbonates have a variation because there are soluble and insoluble carbonates. But when we study deeply about solubility of metal carbonates, most of the carbonates are insoluble in water.

From alkali metals, only lithium forms insoluble carbonate. Li₂CO₃ is a white solid precipitate compound.

All alkaline earth metals forms insoluble carbonate. Also, all 3d metal cations' carbonates are insoluble in water.

Now we list precipitates of carbonate ion with their colours.

• PbCO₃ - white
• ZnCO₃ - white
• FeCO₃ - white

Identify carbonate ion in compounds - qualitative analysis

Precipitates of sulfate ion and colours

Most compounds of sulfate ion ( SO₄^2- ) are soluble in water. Some precipitates and their colours are listed below. Sulfate precipitates are not soluble in dilute acids.

BaSO₄ - barium sulfate - white

SrSO₄ - strontium sulfate - white

CaSO₄ precipitates in higher concentrations and it is also a white precipitate.

Precipitates of sulfite ion | SO₃^2-

Precipitates formed by sulfite ions are dissolved in dilute acids.

• BaSO₃ - barium sulfite - white
• PbSO₃ - lead sulfite - white

Phosphate ion precipitates and colours

Silver phosphate ( Ag₃PO₄ ) is yellow precipitate and dissolve in dilute nitric acid and ammonia.

Barium phosphate ( Ba₃(PO₄)₂ ), the white precipitate dissolve in HCl.

Ferric phosphate - FePO₄ - yellow precipitate - dissolve in HNO₃ and not dissolve in CH₃COOH.

Identify phosphate ion in compounds - qualitative analysis

Halide ion precipitates and colours

Chloride, bromide, iodide ions form precipitates with Ag⁺ and Pb²⁺ ions.

Chloride ion precipitates and colours

• AgCl - white
• PbCl₂ - white
• Hg₂Cl₂ - white

bromide ion precipitates and colours

• AgBr - light yellow
• PbBr₂ - white cream

precipitates and colours of iodide ion

• AgI - yellow
• PbI₂ - yellow

Identify halide ions in compounds - qualitative analysis

Effect of ksp value for precipitation

ksp value give a very clear clarification about precipitation

According to the ksp value, we can decide whether a solid will be precipitated or not.

But, here we don't focus on ksp value. We mainly present you a list of precipitates and their colours.

Colours of anions and cations

Accoring to the anion or cation, colour can be vary.

According to the cation

Ferrous chloride and Ferric chloride

Chloride ion (anion) is common for both compounds. But their colours are different. However, ferrous chloride and ferric chloride are soluble in water.

• Ferrous chloride (FeCl₂) - colourless or green
• Ferric chloride - (FeCl₃) - brown or colour

According to the anion

Lets consider lead +2 ion. PbI₂ is yellow colour precipitate and PbCl₂ is white precipitate. So when anion vary, color of preciptate also vary.

Does nitrate ion form precipitates with cations?

All nitrate compounds are soluble in water. That means, there are no precipitates of nitrate compounds. Also this is same for nitrous ion.

Nitrate ion: NO₃^-

Nitrous ion: NO₂^-

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Questions asked by students

Ask your question and find the answer free.

Which anion will form a precipitate with Ba2+?

Ba²⁺ ion form precipitates with anions such as sulfate, sulfite and carbonate. Therefore, barium carbonate, barium sulfate and barium sulfite are white precipitates.

how to tell if a yellow precipitate is SnS₂ or has CdS as well

Yes. Due to both compounds are yellow color, you have to do furthermore experiments to identify compounds. In SnS₂, Sn⁴⁺ ion exists and CdS contains Cd²⁺ ion. Both compounds include sulfide ion.

1. Add HCl acid separately to both precipitates. Hydrogen sulfide gas will be released from both solutions and two colorless solutions will be given.
2. Then add aqueous NaOH to two solutions. Two white precipitates are given in two flask.
3. Add excess NaOH to white precipitates. One precipitates (Sn(OH)_4(s)) will dissolve in excess NaOH.

what chemicals from with OH to give a white precipitate?

Most metal hydroxides are insoluble except alkali metals and Sr, Ba.

Magnesium, calcium, zinc, lead, aluminium ions will give white precipitates with OH^- ions.

Can you separate compounds by checking only precipitates?

Assume that, there are two compounds which are not soluble in water and have same colour. Then we have to find a another method to separate those kind of compounds.

What are the precipitations of s block group 1 elements

From s block elements, some lithium compounds form precipitates. Also sodium biocarbonate has low solubility in water.

Precipitates of lithium

• Li₂CO₃
• LiF
• Li₂C₂O₄

Which anions form precipitates with s block group 2 elements?

All carboates of s block group 2 elements are precipitates.

Sulfates of Ba²⁺ and Sr²⁺ are precipitates. Hydroxide of Mg²⁺ is a precipitate.

Can colours of precipitates be used everytime to identify compounds?

Cannot. Some precipitates have same colour. As an example, both SrSO₄ and BaSO₄ are white precipitates. Therefore, we cannot identify or separate SrSO₄ and BaSO₄ by considering only colour.

Is aluminium carbonate a precipitate in water and what is the colour?

Aluminium carbonate is not a stable compound and does not exist.

What is the SrSO₄ precipitate colour?

White. SrSO₄ and BaSO₄ are white precipitates.

What are the yellow precipitates?

AgI, PbI₂ are yellow and AgBr is yellow light. CdS and SnS₂ are also yellow precipitates.

Are there any precipitate of sodium ion?

Solubility of sodium bicarbonate | NaHCO₃

Solubility of NaHCO₃ is low. This is used in sodium carbonate production. NaHCO₃ is heated to take Na₂CO₃.

Which metal hydroxide is pink in colour

Manganese hydroxide ( Mn(OH)₂) is a pink colour precipitate.

What is the colour of PbBr₂ precipitate?

White cream precipitate.

Common precipitates in the laboratory?

In the laboratory, we can produce precipitates such as CaCO₃ easily. Send CO₂ gas to the Ca(OH)₂ aqueous solution. Then we can see, a white precipiates forms at the bottom of the solution.

Alkali metals do they form precipitates?

Lithium form some precipitates than other alkali metals. Lithium carbonate, lithium fluoride and lithium phosphate are precipitates.

common precipitate colors

Precipitates are in many colors. Alkali earth metal precipitaes are white while 3d metal precipitates are have so many colours.

What can produce yellow and white precipitates?

Some metal sulfides are yellow colour. So adding some cations to aqueous sulfide ion solution, you can see yellow colour precipitates.

Yellow colour metal sulfides

• CdS
• SnS₂

BaCrO₄ is a yellow precipitate.

what colour does a precipitate have?

Precipitates have different colours.

precipitate color of anion

According to the anion, colour of precipitate can be varied at sometimes. As an example, PbCl₂ is a white precipitate and PbI₂ is a yellow precipitate.

CuSO₄ and NH₄Cl precipitate color

Mixing CuSO₄ and NH₄Cl will give no precipitate.

Related Tutorials

Solubility of inorganic Compounds, s,p,d block elements