51. Which of the following is an example of a colloidal solution in which a solid is dispersed in a solid?
- a) Foam
- b) Gel
- c) Solid sol
- d) Aerosol
Answer: c) Solid sol
Explanation: A solid sol is a colloidal system where solid particles are dispersed in a solid medium. Examples include colored gemstones and some alloys.
52. The removal of colloidal particles from water is done by adding alum. This process is known as:
- a) Electrophoresis
- b) Coagulation
- c) Peptization
- d) Ultrafiltration
Answer: b) Coagulation
Explanation: The process of adding alum to water to remove colloidal impurities is called coagulation. Alum neutralizes the charges on the colloidal particles, causing them to clump together and settle down, making it easier to filter the water.
53. Which of the following is a lyophilic colloid?
- a) Arsenic sulfide sol
- b) Gold sol
- c) Gelatin
- d) Sulphur sol
Answer: c) Gelatin
Explanation: Lyophilic colloids have a strong affinity for the dispersion medium. Gelatin is an example of a lyophilic colloid, as it readily forms a colloidal solution in water and is highly stable.
54. Which of the following statements is incorrect about emulsions?
- a) Emulsions are a type of colloidal system
- b) An emulsifying agent is necessary to stabilize an emulsion
- c) Emulsions cannot be separated into their constituent liquids
- d) Milk is an example of an emulsion
Answer: c) Emulsions cannot be separated into their constituent liquids
Explanation: Emulsions can be separated into their constituent liquids through processes like heating, freezing, or centrifugation. The other statements are correct about emulsions.
55. In an emulsion of water and oil, if water is the dispersed phase, it is known as:
- a) Water-in-oil emulsion
- b) Oil-in-water emulsion
- c) Oil-water gel
- d) Water-water colloid
Answer: a) Water-in-oil emulsion
Explanation: When water is dispersed in oil, it forms a water-in-oil emulsion. Butter and margarine are examples of this type of emulsion.
56. Which of the following is not a property of colloids?
- a) They are homogeneous
- b) They show the Tyndall effect
- c) They exhibit Brownian movement
- d) They cannot be filtered through ordinary filter paper
Answer: a) They are homogeneous
Explanation: Colloidal solutions are heterogeneous in nature, even though the dispersed particles are small enough to appear homogeneous to the naked eye. They do exhibit the Tyndall effect, Brownian movement, and cannot be filtered using ordinary filter paper.
57. The process by which a colloid is converted into a precipitate by adding an electrolyte is called:
- a) Peptization
- b) Coagulation
- c) Dialysis
- d) Ultrafiltration
Answer: b) Coagulation
Explanation: Coagulation is the process of converting a colloidal sol into a precipitate by adding an electrolyte. The electrolyte neutralizes the charges on the colloidal particles, causing them to aggregate and settle down.
58. Which of the following factors does not affect the stability of a colloid?
- a) Size of the colloidal particles
- b) Charge on the colloidal particles
- c) Type of solvent used
- d) Presence of a stabilizer
Answer: c) Type of solvent used
Explanation: The stability of a colloid depends on the size and charge of the colloidal particles and the presence of stabilizers (such as emulsifying agents). The type of solvent does not directly affect the stability of a colloid, though it may affect the dispersion.
59. Which of the following will not cause the coagulation of a colloidal solution?
- a) Adding an electrolyte
- b) Boiling
- c) Freezing
- d) Addition of a protective colloid
Answer: d) Addition of a protective colloid
Explanation: Protective colloids stabilize colloidal solutions and prevent coagulation. The addition of an electrolyte, boiling, or freezing the colloid can cause coagulation by reducing the stability of the colloidal particles.
60. Which of the following describes the Tyndall effect?
- a) The random movement of colloidal particles
- b) The settling down of particles in a colloid
- c) The scattering of light by colloidal particles
- d) The process of coagulation in colloidal solutions
Answer: c) The scattering of light by colloidal particles
Explanation: The Tyndall effect refers to the scattering of light by colloidal particles. This effect is observed when a beam of light passes through a colloidal solution and becomes visible due to the scattering.
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