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प्रश्न
How do emulsifying agents stabilise the emulsion?
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उत्तर
Emulsifying agents stabilize the emulsion by forming an interfacial film between suspended particle and dispersion medium. For example, agar is an emulsifying agent used in food.
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संबंधित प्रश्न
Define the following with a suitable example, of each:
Gel
Choose the correct option.
The size of colloidal particles lies between ______.
Explain the term emulsion and types of emulsions.
Which type of colloid is formed on the dissolution of soap in water?
Which of the following is multimolecular colloid?
Which of the following is a heterogeneous mixture?
Which of the following is an example of liquid-liquid system?
Which of the following is NOT true for lyophilic colloids?
Tyndall effect is useful ______.
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
What happens when electric field is applied to colloidal solution?
Why are some medicines more effective in the colloidal form?
On the basis of Hardy-Schulze rule explain why the coagulating power of phosphate is higher than chloride.
Why does bleeding stop by rubbing moist alum?
Colloids can
Which of the following substances will precipitate the negatively charge emulsion
Smoke is an example of ______.
Which of the following electrolytes will be most effective in coagulating negative sol?
