Advertisements
Advertisements
प्रश्न
Distinguish between lyophobic and lyophilic sols.
What are the main points of difference between lyophilic and lyophobic sols?
Advertisements
उत्तर
| Sr. No. | Points | Lyophobic sols | Lyophilic sols |
| 1. | Method of formation | Lyophobic sols are formed only by special methods. | Lyophilic sols are formed easily by direct mixing. |
| 2. | Reversibility | They are irreversible. | They are reversible. |
| 3. | Stability | These are unstable and hence, require traces of stabilizers. | These are self-stabilized. |
| 4. | Effect of electrolytes | The addition of a small amount of electrolytes causes precipitation or coagulation of lyophobic sols. | The addition of a large amount of electrolytes causes precipitation or coagulation of lyophilic sols. |
| 5. | Viscosity | The viscosity of lyophobic sol is nearly the same as the dispersion medium. | The viscosity of lyophilic sol is much higher than that of the dispersion medium. |
| 6. | Surface tension | The surface tension of lyophobic sol is nearly the same as the dispersion medium. | The surface tension of lyophilic sol is lower than that of the dispersion medium. |
APPEARS IN
संबंधित प्रश्न
Choose the correct option.
The size of colloidal particles lies between ______.
Write a note on the Tyndall effect.
Explain Electrophoresis diagramatically.
Explain Bredig’s arc method.
Explain the term emulsion and types of emulsions.
Explain micelle formation in a soap solution.
Draw labelled diagram Dialysis.
Draw labelled diagram of Bredig’s arc method.
Draw labelled diagram of Soap micelle.
Which of the following is multimolecular colloid?
In coagulation of positively charged ferric hydroxide sol, the most and least effective ions are ____________ and ____________ respectively.
Which of the following is NOT true for lyophilic colloids?
Mixing of two oppositely charged sols leads to ____________.
Which of the following is multimqlecular colloid?
Tyndall effect is useful ______.
Pumice stone is an example of ______.
Some colloids are stable by their nature, i.e., gels, alloys, and solid foams. Gelatin and jellies are two common examples of a gel. The solid and liquid phases in a gel are interdispersed with both phases being continuous. In most systems, the major factor influencing the stability is the charge on the colloidal particles. If a particular ion is preferentially adsorbed on the surface of the particles, the particles in suspension will repel each other, thereby preventing the formation of aggregates that are larger than colloidal dimensions. The ion can be either positive or negative depending on the particular colloidal system, i.e., air bubbles accumulate negative ions, sulphur particles have a net negative charge in a sulphur sol, and the particles in a metal hydroxide sol are positively charged. Accumulation of charge on a surface is not an unusual phenomenon-dust is attracted to furniture surfaces by electrostatic forces. When salts are added to lyophobic colloidal systems the colloidal particles begin to form larger aggregates and a sediment forms as they settle. This phenomenon is called flocculation, and the suspension can be referred to as flocculated, or colloidally unstable. If the salt is removed, the suspension can usually be restored to its original state; this process is called deflocculation or peptization. The original and restored colloidal systems are called deflocculated, peptized, or stable sols.
Why does a small amount of salt have such a dramatic effect on the stability of a lyophobic colloidal system? The answer lies in an understanding of the attractive and repulsive forces that exist between colloidal particles. Van der Waals forces are responsible for the attractions, while the repulsive forces are due to the surface charge on the particles. In a stable colloid, the repulsive forces are of greater magnitude than the attractive forces. The magnitude of the electrical repulsion is diminished by addition of ionized salt, which allows the dispersed particles to aggregate and flocculate. River deltas provide an example of this behaviour. A delta is formed at the mouth of a river because the colloidal clay particles are flocculated when the freshwater mixes with the salt water of the ocean.
Colloidal solutions are stable due to ______.
A colloidal system having a solid substance as a dispersed phase and a liquid as a dispersion medium is classified as ______.
Which of the following process is responsible for the formation of delta at a place where rivers meet the sea?
A colloid is formed by adding \[\ce{FeCl3}\] in excess of hot water. What will happen if excess sodium chloride is added to this colloid?
Why does bleeding stop by rubbing moist alum?
Match the items of Column I and Column II.
| Column I | Column II |
| (i) Butter | (a) dispersion of liquid in liquid |
| (ii) Pumice stone | (b) dispersion of solid in liquid |
| (iii) Milk | (c) dispersion of gas in solid |
| (iv) Paints | (d) dispersion of liquid in solid |
Cloud is an example of
Which of the following electrolytes will be most effective in coagulating negative sol?
Blood may be purified by ______.
Identify positively charged sol from following.
