Question

The coagulation power of an electrolyte for blood decreases in the order:
A. $N{a^ + },B{a^{2 + }},A{l^{3 + }}$
B. $PO_4^{3 - },SO_4^{2 - },C{l^ - }$
C. $A{l^{3 + }},B{a^{2 + }},N{a^ + }$
D. $C{l^ - },SO_4^{2 - },PO_4^{3 - }$

Answer 1

Blood is a colloidal solution containing negative charged colloidal particles( albuminoid) . The factors affecting coagulation power are nature of sols, nature of electrolyte and hardy Schultz rule. Strong electrolytes have greater coagulating power than weak electrolytes.

Complete step by step answer:
Let us understand Hardy Schultz rule, According to this rule greater the valency of the coagulating ion, greater is the power to cause precipitation. Active ion is responsible for coagulation.
Coagulation or flocculating value is the minimum concentration of electrolyte in millimoles required to cause coagulation of one litre of colloidal solution. Since in the options we are given with anions we must know the coagulating power of anion. So greater the charge on an anion greater is its coagulating power.
But as we know that Blood is negatively charged sol. So a positively charged ion is capable of coagulating blood. Since coagulation is the process of aggregation of colloidal particles into an insoluble precipitate by the addition of some suitable electrolyte such as the particles are neutral.in case of negatively charged sol the coagulating power of cation increases as the charge on cation increases According to Hardy Schulze rule, greater the valency of coagulating ion greater is the coagulation power. So order of coagulation power is $A{l^{3 + }} > B{a^{2 + }} > N{a^ + }$

Hence the correct option is C.

Note:
That process includes coagulation, a step in which chemicals are added that cause small particles suspended in the water to clump together. Coagulants are added to the water to bring the non-settling particles together into larger, heavier masses of solids called floc. Arsenious sulphide is negatively charged sol, hence it will be coagulated by positive ion having maximum amount of charge hence $Al^{3+}$ have maximum coagulating power.