81. Which of the following methods cannot be used for the coagulation of a lyophilic colloid?
- a) Addition of electrolyte
- b) Addition of an oppositely charged sol
- c) Heating
- d) Adding a protective colloid
Answer: d) Adding a protective colloid
Explanation: Adding a protective colloid stabilizes the colloidal solution and prevents coagulation. The other methods, such as adding an electrolyte, heating, or adding an oppositely charged sol, can cause coagulation.
82. Which of the following is an example of a colloid in which a gas is dispersed in a liquid?
- a) Foam
- b) Emulsion
- c) Sol
- d) Smoke
Answer: a) Foam
Explanation: Foam is a colloidal system in which gas is dispersed in a liquid. Examples include whipped cream and soap lather.
83. Which of the following is used as an emulsifying agent in the preparation of emulsions?
- a) Gelatin
- b) Ferric hydroxide
- c) Starch
- d) Water
Answer: a) Gelatin
Explanation: Gelatin is used as an emulsifying agent to stabilize emulsions by forming a protective layer around the dispersed droplets, preventing them from coalescing.
84. Which of the following is an example of a negatively charged colloid?
- a) Gold sol
- b) Ferric hydroxide sol
- c) Arsenic sulphide sol
- d) Silver iodide sol
Answer: c) Arsenic sulphide sol
Explanation: Arsenic sulphide sol carries a negative charge due to the absorption of sulphide ions (S²⁻) on the surface of the colloidal particles, making it a negatively charged colloid.
85. Which of the following is not a method of purifying colloidal solutions?
- a) Dialysis
- b) Ultrafiltration
- c) Coagulation
- d) Electrodialysis
Answer: c) Coagulation
Explanation: Coagulation is the process of causing colloidal particles to aggregate and settle out, leading to the breakdown of the colloidal solution. It is not used for purifying colloids. Dialysis, ultrafiltration, and electrodialysis are purification methods.
86. Which of the following describes the Brownian movement?
- a) The scattering of light by colloidal particles
- b) The random zig-zag motion of colloidal particles
- c) The process of coagulation of colloids
- d) The adsorption of ions on the surface of colloidal particles
Answer: b) The random zig-zag motion of colloidal particles
Explanation: Brownian movement refers to the random, zig-zag motion of colloidal particles in a dispersion medium, caused by the continuous collisions with the molecules of the medium.
87. Which of the following types of colloids can be prepared by both dispersion and condensation methods?
- a) Lyophobic colloids
- b) Lyophilic colloids
- c) Macromolecular colloids
- d) Associated colloids
Answer: a) Lyophobic colloids
Explanation: Lyophobic colloids (solvent-hating) can be prepared by both dispersion (breaking down large particles into colloidal size) and condensation (building up particles from smaller units) methods.
88. Which of the following is an example of a multimolecular colloid?
- a) Gold sol
- b) Starch sol
- c) Soap sol
- d) Sulphur sol
Answer: d) Sulphur sol
Explanation: A multimolecular colloid consists of an aggregate of many small molecules. Sulphur sol is a multimolecular colloid, where many sulphur molecules aggregate to form colloidal particles.
89. Which of the following methods is used to convert a precipitate into a colloidal solution?
- a) Coagulation
- b) Peptization
- c) Electrophoresis
- d) Dialysis
Answer: b) Peptization
Explanation: Peptization is the process of converting a precipitate into a colloidal solution by adding a small amount of electrolyte, which helps to break the precipitate into colloidal particles.
90. Which of the following colloids is used in the preparation of medicines due to its high adsorption capacity?
- a) Lyophilic colloids
- b) Lyophobic colloids
- c) Associated colloids
- d) Macromolecular colloids
Answer: a) Lyophilic colloids
Explanation: Lyophilic colloids have a high adsorption capacity because of their strong affinity for the dispersion medium. This property makes them useful in the preparation of medicines to increase the stability of drug formulations.
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