Question

Bleeding from a wound stops by the application of ${\mathrm{FeCl}}_3$ solution. Which of the following phenomenon takes place due to the same reason?

• A. Dust particles present in the air become visible due to the passage of a narrow beam of light in a dark room.
• B. Some syrupy medicines are advised to be taken after shaking the bottle.
• C. A supersaturated solution slowly becomes transparent.
• D. Addition of alum hastens the process of purification of water.

Answer 1

The correct option is D

Addition of alum hastens the process of purification of water.

Explanation of correct option:

• In order to stop bleeding in cuts, Ferric chloride ($FeC{l}_3$) is used because Iron coagulates blood because blood is a negatively charged colloidal solution.
• By rubbing the injured part with ${\mathrm{Fe}}^{3+}$, blood coagulates.
• Therefore, coagulation stops bleeding.
• Aluminum helps in purifying water by coagulating mud particles. Due to the high charge on the aluminum ion (${\mathrm{Al}}^{3+}$), the small particles of suspended solids will gather until they are large enough to sink and can be removed.

Hence, the correct option is (D).