Question

Assertion: Alum is used to stop blood from a cut.
Reason: Blood is negative sol and sol particles are coagulated more efficiently by AL3+ions.
A. Both Assertion and reason are correct and reason is the correct explanation for Assertion.
B. Both Assertion and reason are correct but reason is not the correct explanation for assertion.
C. Assertion is correct but reason is incorrect.
D. Assertion is incorrect but reason is correct.

Answer 1

For solving this question, we need to understand the properties of colloids. The size of particles of a colloid is too small to be individually seen by naked eyes and they are heterogeneous mixtures. Also, they are big enough which scatters a beam of light passing through it and makes its path visible. They do not settle down when left undisturbed. So, colloids are quite stable.

Complete step by step answer:
Alum is used to stop blood from a cut. It acts as a hemostatic agent, allowing the blood clot to form. The blood gets flocculation due to having greater ionic strength and the astringent chemical causes local vasoconstriction. Thus, blood is negative sol and sol particles are coagulated more efficiently by $Al^{3+}$ ions. So, both the assertion and reasons are correct and reason is the correct explanation for Assertion (option A).
We can use Alum block on cuts during or after shaving because Alum has Kashaya which has astringent properties and which has hemostatic properties. So, these properties can stop bleeding as quickly as it is rubbed on the affected area. As alum have astringent and antiseptic properties. So, it can be used to inhibit body odor when used as natural deodorant.

So, the correct answer is Option A.

Note: We know that potash alum or potassium alum is potassium double sulfate of aluminum. It is astringent, styptic and antiseptic. Its astringent and styptic properties are often employed as after shaving and to reduce bleeding in minor cuts and abrasions a pinch of alum can kill bacteria from water.