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 


(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 

charges over them.

It is possible to cause artificial rain by throwing electrified sand or spraying

a sol carrying charge 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 adsortion, 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 in direct 

contact with the surface of the adsorbent, hence this type of adsorption

is mono-layered.

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