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प्रश्न
Write a note on Brownian motion.
उत्तर
- The colloidal or microscopic particles undergo ceaseless random zig-zag motion in all directions in a fluid. This motion of dispersed phase particles is called Brownian motion.
- Cause of Brownian motion:
- Particles of the dispersed phase constantly collide with the fast-moving molecules of the dispersion medium (fluid).
- Due to this, the dispersed phase particles acquire kinetic energy from the molecules of the dispersion medium.
- This kinetic energy brings about Brownian motion.
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संबंधित प्रश्न
Define the following with a suitable example, of each:
Multimolecular colloid
Define the following with a suitable example, of each:
Gel
Distinguish between Lyophobic and Lyophilic sols.
Explain Electrophoresis diagramatically.
Explain the term emulsion and types of emulsions.
Draw labelled diagram Tyndall effect.
Draw labelled diagram of Bredig’s arc method.
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 an example of liquid-liquid system?
Maximum coagulation power is in ____________.
Which of the following is NOT true for lyophilic colloids?
Which of the following is multimqlecular colloid?
Tyndall effect is useful ______.
The movement of colloidal particles towards respective electrode under electric field is called ______.
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.
Freshly prepared precipitate sometimes gets converted to colloidal solution by ______.
Which of the following process is responsible for the formation of delta at a place where rivers meet the sea?
Which of the following substances will precipitate the negatively charged emulsions?
(i) \[\ce{KCl}\]
(ii) glucose
(iii) urea
(iv) \[\ce{NaCl}\]
What happens when electric field is applied to colloidal solution?
Why does bleeding stop by rubbing moist alum?
Colloids can
Toluene is oxidised to benzoic acid by
Which of the following substances will precipitate the negatively charge emulsion
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?
Which of the following is most powerful to coagulate the negative colloid?
Blood may be purified by ______.
Identify the colloidal molecule containing hydrophilic head and hydrophobic tail within it.
