Question

Bleeding from a fresh cut can be stopped by applying alum give reason for your answer

Answer 1

Bleeding can be stopped by coagulation of the blood (formation of a clot). This coagulation is the process of aggregation of the colloidal solution of protein in blood. Proteins are charged species and their aggregation or coming together depends on the neutralization (partial or complete) of the charges on the protein molecules. This can be accomplished by soluble charged species or ions in water. Now, if an ion has a high charge density it is more capable of neutralizing charges on the protein or any charged colloid. Potash alum has highly charged Al3+ and (SO4)2- ions which act as neutralizing ions for the protein colloid in blood. This causes aggregation or clotting and this in turn stops the bleeding.