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प्रश्न
Explain Bredig’s arc method.
उत्तर
- Colloidal sols can be prepared by electrical disintegration using Bredig’s arc method.
- This process involves vaporization as well as condensation.
- Colloidal sols of metals such as gold, silver, platinum can be prepared by this method.
- In this method, an electric arc is struck between electrodes of metal immersed in the dispersion medium.
- The intense heat produced vapourizes the metal which then condenses to form particles of colloidal sol.
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संबंधित प्रश्न
Write one difference in Multimolecular colloid and Associated colloid
Define the following with a suitable example, of each:
Multimolecular colloid
Choose the correct option.
The size of colloidal particles lies between ______.
Write a note on Brownian motion.
Write a note on Types of emulsion.
Explain Electrophoresis diagramatically.
Explain micelle formation in a soap solution.
Draw labelled diagram Dialysis.
Which one of the following methods is used to make platinum sol?
Which of the following is multimolecular colloid?
The precipitation power of an electrolyte increases with ______.
Mixing of two oppositely charged sols leads to ____________.
Froth is a colloidal solution of ____________.
Which of the following is multimqlecular colloid?
Tyndall effect is useful ______.
The movement of colloidal particles towards respective electrode under electric field is called ______.
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.
Which of the following electrolytes will have maximum coagulating value for AgI/Ag+ solution?
What happens when electric field is applied to colloidal solution?
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 does the precipitation of colloidal smoke take place in Cottrell precipitator?
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 |
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?
Identify the colloidal molecule containing hydrophilic head and hydrophobic tail within it.
Identify the correct decreasing order of precipitation power of flocculating ion added, from following.
