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प्रश्न
What happens when a beam of light is passed through a colloidal sol.
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उत्तर
- When a beam of light is passed through colloidal sol, it is observed that the colloidal particles scatter some of the incident light in all directions.
- Because of this scattering of light, the path of light through the colloidal dispersion becomes visible to an observer standing at right angles to its path, and the phenomenon is known as the Tyndall effect.
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संबंधित प्रश्न
Define the following with a suitable example, of each:
Multimolecular colloid
Distinguish between lyophobic and lyophilic sols.
Identify the dispersed phase and dispersion medium in the following colloidal dispersions.
- milk
- blood
- printing ink
- fog
Write a note on Types of emulsion.
Draw labelled diagram Dialysis.
Identify the CORRECT statement.
Mist is a colloidal solution of ____________.
In coagulation of positively charged ferric hydroxide sol, the most and least effective ions are ____________ and ____________ respectively.
Which of the following is a heterogeneous mixture?
Which of the following statements is CORRECT?
The precipitation power of an electrolyte increases with ______.
Mixing of two oppositely charged sols leads to ____________.
Smoke is an example of ____________.
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.
Gelatin is a _________ colloidal system.
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.
Settling down of colloidal particles to form a suspension is called ______.
An emulsion cannot be broken by:
(i) heating
(ii) adding more amount of dispersion medium
(iii) freezing
(iv) adding emulsifying agent
Gelatin which is a peptide is added in icecreams. What can be its role?
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?
How do emulsifying agents stabilise the emulsion?
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 |
For coagulating 200 ml of arsenious sulphide sol, 10 ml of 1 m NaCl solution is required find out the flocculation value of NaCl.
The migration of dispersion medium under the influence of an electric potential is called ______.
In which of the following, the Tyndall effect is not observed?
Smoke is an example of ______.
Identify positively charged sol from following.
