100 mL of 5% (w/v) solution of NaCl in water was prepared in 250 mL beaker. Albumin from the egg was poured into NaCl solution and stirred well. This resulted in a/an

We have a 5% (w/v) NaCl solution to which egg albumin is added and stirred. We need to determine the type of colloidal system formed.

Albumin is a protein — a naturally occurring macromolecule. When proteins are dissolved or dispersed in an aqueous medium, they form colloidal solutions. The key question is whether this colloidal sol is lyophilic or lyophobic.

A lyophilic sol (solvent-loving) is one in which the dispersed phase has a strong affinity for the dispersion medium. Proteins like albumin have numerous polar groups ($$-NH_2$$, $$-COOH$$, $$-OH$$) on their surface that readily interact with water molecules through hydrogen bonding. Because of this strong interaction, protein sols form spontaneously when stirred — no special methods are needed, and the resulting sol is quite stable.

A lyophobic sol (solvent-hating), in contrast, is formed by substances like metals or metal sulphides that have no affinity for water. Such sols require special techniques (like Bredig's arc method) to prepare and are inherently unstable.

Since albumin is a protein with strong affinity for water, the dispersion formed is a lyophilic sol. The NaCl solution simply serves as the dispersion medium — at 5% concentration, it is not high enough to salt out the albumin.

Hence, the correct answer is Option A: Lyophilic sol.