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).

Then, CaCO3 and BaSO4 are called as precipitates.


A precipitate in the aqueous solution

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. Other precipitates of anions and cations

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.


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.

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 blocl, 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


precipitates of alkaline earth metals

Alkaline earth metals forms both precipitates and solutions.

  • All carbonates (CO32-) 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

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



Precipitates of 3d metals sulfides with other d block metals and p block metals

  • HgS(s) - black
  • Sb2S3(s) - orange
  • CdS(s) - yellow
  • FeS(s) - black
  • SnS(s) - yellow brown
  • SnS2(s) - yellow
  • CuS(s) - black

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

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

All alkaline earth metals forms insoluble carbonate.

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 ( SO42- ) 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 | SO32-

Precipitates of 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

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.

Examples


According to the cation

Ferrous chloride and Ferric chloride

Chloride ion (anion) is common for both compounds. But their colours are different.

  • 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-



Question of precipitates and colours


Ask you question free and find the answer

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.



Related Tutorials


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