Question

The process which is responsible for the formation of delta at a place where river meets the sea is
(A)Colloid formation
(B)Peptization
(C)Emulsification
(D)Coagulation

Answer 1

Hint :We know that a delta is the deposition of sediments that a river carries along its flow on slower moving or stagnant water bodies like sea, ocean, estuary etc. It is formed at the meeting point of the river and sea. River water is a colloidal solution and the sea contains water and electrolytes.

Complete Step By Step Answer:
River water is a colloidal solution that contains clay, mud, sand, sediments and pebbles whereas sea water is rich in electrolytes. As the river meets the sea, larger particles like sand, mud and pebbles settle down. Clay is negatively charged and has the size in the colloidal range. It forms colloidal sol – solid dispersed in liquid (dispersion medium). Sea water contains many positive electrolytes like \[N{a^ +}\] which neutralises the negatively charged clay leading to a process called coagulation. The process of settling down of colloidal particles is known as coagulation or precipitation of sol. As a result of coagulation, large neutral particles get accumulated and they settle down. This leads to the formation of delta.
The answer is (D) coagulation.

Note :
The stability of lyophobic sols is due to the charge present on them. Therefore, by adding small amounts of oppositely charged electrolyte, neutralisation takes place, leading to coagulation. The ion responsible for coagulation is called coagulating ion. A positive ion precipitates a negative sol.