Question

Addition of potash alum results in the purification of water. The phenomenon associated with this reaction is ____

• A. Precipitation
• B. Crystallization
• C. Coagulation
• D. Sterilization

Answer 1

The correct option is C

Coagulation

Explanation for the correct option:

(C)

• Alum helps in purifying water with aluminum which coagulates the mud particles.
• Chemical name of potash alum is potassium aluminum sulphate.
• Because of the high charge on the aluminum ion (${\mathrm{Al}}^{3+}$), it helps the small particles of suspended solids to group together until they are of such size that they sink and can be removed.

So, this phenomenon occurs due to coagulation.

Explanation for the incorrect options:

(A) Precipitation - In this type of reaction, a substance gets settled at the bottom during the reaction.

(B) Crystallization- During this reaction crystals of products are formed.

(D) Sterilization- It is the process of using low-temperature chemicals to kill, eliminate, and remove all germs, viruses, and bacteria.

Hence, the correct option is (C).