Advertisements
Advertisements
प्रश्न
Write a note on Types of emulsion.
Advertisements
उत्तर
There are two types of emulsions:
- Emulsion of oil in water (o/w type):
An emulsion in which the dispersed phase is oil and the dispersion medium is water is called an emulsion of oil in water.
Example:
- Milk consists of particles of fat dispersed in water.
- Other examples include vanishing cream, paint, etc.
- Emulsion of water in oil (w/o type):
An emulsion in which the dispersed phase is water and dispersion medium is the oil is called emulsion of water in oil.
Example:
- Cod liver oil consists of particles of water dispersed in oil.
- Some other examples of this type include butter, cream, etc.
APPEARS IN
संबंधित प्रश्न
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 the Tyndall effect.
Explain Bredig’s arc method.
Explain the term emulsion and types of emulsions.
Draw labelled diagram of Bredig’s arc method.
Which type of colloid is formed on the dissolution of soap in water?
Froth and whipped cream are examples of ____________.
Identify the CORRECT statement.
In coagulation of positively charged ferric hydroxide sol, the most and least effective ions are ____________ and ____________ respectively.
Which of the following can form colloidal sol with water?
Tyndall effect is useful ______.
The movement of colloidal particles towards respective electrode under electric field is called ______.
Which of the following compounds forms a colloidal solution when dissolved in water?
In which of the following sols there is low affinity between dispersed phase and dispersion medium?
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
Which of the following substances will precipitate the negatively charged emulsions?
(i) \[\ce{KCl}\]
(ii) glucose
(iii) urea
(iv) \[\ce{NaCl}\]
Gelatin which is a peptide is added in icecreams. What can be its role?
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 do emulsifying agents stabilise the emulsion?
Why are some medicines more effective in the colloidal form?
Why does bleeding stop by rubbing moist alum?
The size of a raw mango shrinks to a much smaller size when kept in a concentrated salt solution. Which one of the following processes can explain this?
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.
