Question

Define efflorescence. Give examples.

Answer 1

Hint: We may confuse efflorescence with fluorescence. But it is not at all related with fluorescence or excitation of electrons. But it is only connected with properties of salts. It is something which is connected with surface chemistry.

Complete step by step answer:
Let us first look towards the definition of the term. When salty liquids are moved to a porous material surface, liquid gets evaporated which forms a powder like coating on the surface of the material. This is termed as efflorescence.
Some examples of efflorescent salts are ${{N}}{{{a}}_2}{{S}}{{{O}}_4}.10{{{H}}_2}{{O}}$, ${{N}}{{{a}}_2}{{C}}{{{O}}_3}.10{{{H}}_2}{{O}}$, ${{FeS}}{{{O}}_4}.7{{{H}}_2}{{O}}$ etc.
Now we’ll know more about efflorescence. Efflorescence is observed when there is a content of water molecules in materials like brick, concrete, stone or other buildings. When this water molecule evaporates, there forms some crystals like white powder deposits on the surface of the material. This may appear in floors and walls.
The main causes of efflorescence are rain, snow and water. A major example of efflorescence is gypsum forming a solid crust. When it is kept under a dry environment, the water content in it is lost and there forms a solid crystal on the surface.

Note: Certain buildings may have problems in installation of surface. Masonry must be done with proper ventilation. Proper moisture barrier must be there during masonry works.
Efflorescence can be removed by using brush in smooth surfaces.
Conditions for efflorescence:
The salts present must be water soluble
Moisture content helps to dissolve the salts and form a solution.
These salts should have the ability for the movement to the surface of material.