Adsorption is the phenomenon of attracting and retaining the molecules of a substance on the surface of a solid resulting into a higher concentration on the surface than in the bulk. The substance adsorbed is known as adsorbate and the substance on which adsorption takes place is called adsorbent. In physisorption adsorbate is held to the adsorbent by weak van der Waals forces and in chemisorption by strong chemical bond.

In coagulation of a positive sol, the flocculating power will be in the order

1. \(PO_4^{3-}\)
2. \(Cl^-\)
3. \(Fe(CN_6)^{4-}\)
4. \(SO_4^{2-}\)

Choose the correct answer from the options given below:

C > A > D > B

The flocculating power of an ion in a coagulation process depends on the charge of the ion and its valency. In general, ions with higher charges and higher valencies have higher flocculating powers.

Given the different ions mentioned in the question:

• \(Fe(CN_6)^{4-}\) has the highest charge \(4^-\) and highest valency \(4\).
• \(PO_4^{3-}\) has a charge of \(3^-\) and a valency of \(3\).
• \(SO_4^{2-}\) has a charge of \(2-\) and a valency of \(2\).
• \(Cl^-\) has a charge of \(1^-\) and a valency of \( 1\).

Therefore, the order of flocculating power is:

\(Fe(CN_6)^{4-} > PO_4^{3-} > SO_4^{2-} > Cl^-\)

This corresponds to the answer choice 1. C > A > D > B.