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प्रश्न
Write a note on the Tyndall effect.
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उत्तर
- Tyndall observed that when light passes through a true solution, the path of light through it cannot be detected.
- However, if the light passes through a colloidal dispersion, the particles scatter some light in all directions and the path of the light through colloidal dispersion becomes visible to an observer standing at right angles to its path.
- The phenomenon of scattering of light by colloidal particles and making the path of light visible through the dispersion is referred to as the Tyndall effect and the bright cone of the light is called the Tyndall cone.
- The Tyndall effect is observed only when the following conditions are satisfied.
a. The diameter of the dispersed particles is not much smaller than the wavelength of light used.
b. The refractive indices of the dispersed phase and dispersion medium differ largely. - Significance of Tyndall effect:
a. It is useful in determining the number of particles in the colloidal system and their particle size.
b. It is used to distinguish between colloidal dispersion and true solution.
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संबंधित प्रश्न
Comment on the statement that “colloid is not a substance but a state of substance”.
Define the following with a suitable example, of each:
Gel
Identify the dispersed phase and dispersion medium in the following colloidal dispersions.
- milk
- blood
- printing ink
- fog
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What happens when a beam of light is passed through a colloidal sol.
Explain the term emulsion and types of emulsions.
Draw labelled diagram Tyndall effect.
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Which one of the following methods is used to make platinum sol?
Identify the CORRECT statement.
Identify the CORRECT statements from the following.
i. The colour of colloidal dispersion depends on size of colloidal particles.
ii. Tyndall effect is used to distinguish between colloidal dispersion and true solution.
iii. Eosin and congo red are examples of negatively charged sols.
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?
The precipitation power of an electrolyte increases with ______.
Pumice stone is an example of ______.
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Which of the following electrolytes will have maximum coagulating value for AgI/Ag+ solution?
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?
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?
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.
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 |
Colloids can
Toluene is oxidised to benzoic acid by
Fog is a colloidal solution of ______.
The migration of dispersion medium under the influence of an electric potential is called ______.
Blood may be purified by ______.
Starch is an example of which of the following type of colloid?
