NEET Chemistry Surface Chemistry Questions Solved


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 

is mono-layered.

(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

over them.

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.


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