Explain the following:
(i) Deltas are formed when river and sea water meet.
(ii) Artificial rain is caused by spraying salt over clouds.
(iii) Physisorption is multi-layered, while chemisorption
(i) River Water is a colloidal solution of clay. Sea water contains a number
of electrolytes. When river water meets the sea water, the electrolytes present
in sea water coagulate the colloidal solution of clay resulting in its deposition
with the formation of deltas.
(ii) Clouds are colloidal dispersion of water particles in air carrying some charge
It is possible to cause artificial rain by throwing electrified sand or spraying a sol
carrying charge is opposite to the one on clouds from an aeroplane.
The colloidal water particles present in the clouds will get neutralized and as result
they will come closer and grow in size to form bigger water drops and ultimately
cause artificial rain.
(iii) In physical adsorption, layers of the gas can be adsorbed one over the other
by van der Waals forces. Multi-molecular layers are formed under high pressure.
In chemical adsorption, chemical bond can be formed only with the layer of
molecules coming into direct contact with the surface of the adsorbent, hence
this type of adsorption is mono-layered.