A sample of red ink (a colloidal suspension) is prepared by mixing eosin dye, egg white, HCHO and water. The component which ensures stability of the ink sample is :

Solution

Chemistry ma’am · 3 steps

Ask which component wraps the colloid particles and stops them clumping: that is the protective colloid.

1. Role of each part. Each component of the ink does a different job. Only one of them keeps the dispersed particles from coagulating, and that one gives stability.

   Component	Job in the ink
   Eosin dye	gives the red colour
   Water	dispersion medium
   HCHO	preservative, stops microbes from spoiling the egg white
   Egg white	protective colloid (lyophilic sol), stabilises the ink

2. Protective colloid. Egg white is a protein, so it forms a lyophilic sol. Its molecules form a layer around the colloid particles, which are less stable on their own. This layer shields them from coagulation.
3. So. Egg white is the component that keeps the ink stable, which is option (d).

The idea to keep. Colloids that are less stable on their own (lyophobic sols) are protected by a lyophilic colloid such as gelatin, egg albumin or gum. Whenever a question asks what stabilises a sol, look for the protective colloid.

Answer from the NTA final answer key. Solution by PrepWiser.