Question

What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?

Answer 1

Lyophobic and lyophilic sols are categorised in the colloids on the basis of dispersed phase, and the dispersion medium. The concept of coagulation is related to the presence of charge on the colloidal sols. Now, we can explain it.

Complete step by step answer:
- Now, we will discuss the lyophilic sols, and lyophobic sols.
- First, we have lyophilic sols. The sols obtained by combining substances in dispersion medium, and the interaction between the dispersed phase, and the dispersion medium are strong.
- Due to the strong interactions, the lyophilic sols are considered to be stable, and these are also named as reversible sols.
- The hydration ability of lyophilic sols is high. Since its hydration value is high, the viscosity of the Lyophilic sols is also higher than the medium.
Their surface tension is usually lower than the surface tension of the dispersion medium.
The examples of lyophilic sols are rubber, and starch.

Second, we have the lyophobic sols. These sols cannot be attained by the simple mixing; it will be formed by applying the electrolyte, and they need to be heated for the formation of sols.
So, the lyophobic sols are unstable in nature.
- The hydration ability of lyophobic sols is low. Since, its hydration value is low, the viscosity of the Lyophobic sols is almost the same as that of the medium.
- Their surface tension is usually the same as that of the surface tension of the dispersion medium.
The examples are ferric hydroxide dissolved in water.
Now, we have to explain the reason behind the easy coagulation of hydrophobic sols.

Lyophilic sols	Lyophobic sols
Since, the stability of the Lyophilic sols is high they are not easily coagulated into larger molecules	These are not stable, they will combine to form molecules having large molecules, even with the addition of the small amount of suitable electrolyte.

Note: Don’t get confused with the coagulation of sols. The lyophobic sols are also stabilized by the adsorption of charge or ions present in the sol by the dispersed particles, and that’s why these are irreversible in nature.