71. Which of the following is an example of a macromolecular colloid?
- a) Sulphur sol
- b) Gold sol
- c) Starch sol
- d) Arsenic sulphide sol
Answer: c) Starch sol
Explanation: A macromolecular colloid is a colloidal solution in which large molecules form the dispersed phase. Starch sol is an example of a macromolecular colloid due to the large size of starch molecules.
72. What is the role of soap in the cleaning process?
- a) Soap coagulates dirt particles
- b) Soap neutralizes the charge on dirt particles
- c) Soap forms micelles that trap dirt particles
- d) Soap increases the viscosity of water
Answer: c) Soap forms micelles that trap dirt particles
Explanation: Soap molecules form micelles when dissolved in water. The hydrophobic tails of the soap molecules surround dirt and grease particles, trapping them in the micelle, which is then washed away with water.
73. Which of the following methods is used to remove colloidal impurities from water in water treatment plants?
- a) Adsorption
- b) Coagulation
- c) Ultrafiltration
- d) Electrophoresis
Answer: b) Coagulation
Explanation: In water treatment plants, coagulation is used to remove colloidal impurities. Coagulants like alum are added, which neutralize the charge on colloidal particles, causing them to clump together and settle.
74. Which of the following statements is true regarding lyophobic colloids?
- a) They are reversible
- b) They have a strong affinity for the dispersion medium
- c) They require stabilizing agents
- d) They do not exhibit Tyndall effect
Answer: c) They require stabilizing agents
Explanation: Lyophobic colloids (solvent-hating) do not have a natural affinity for the dispersion medium and require stabilizing agents to prevent coagulation. They are generally irreversible and exhibit the Tyndall effect.
75. Which of the following colloids is used as a protective colloid?
- a) Gold sol
- b) Gelatin
- c) Starch
- d) Sulphur sol
Answer: b) Gelatin
Explanation: Gelatin is commonly used as a protective colloid. It stabilizes colloidal sols by preventing them from coagulating when electrolytes are added.
76. Which of the following statements is incorrect regarding emulsions?
- a) Emulsions are a type of colloidal solution
- b) They can be separated by mechanical means like centrifugation
- c) Emulsions are stable without emulsifying agents
- d) Oil-in-water and water-in-oil are two types of emulsions
Answer: c) Emulsions are stable without emulsifying agents
Explanation: Emulsions generally require emulsifying agents to stabilize the dispersed droplets and prevent them from separating. Without emulsifying agents, emulsions tend to separate over time.
77. The charge on colloidal particles is due to:
- a) Absorption of ions from the solution
- b) Electrophoresis
- c) Tyndall effect
- d) Brownian movement
Answer: a) Absorption of ions from the solution
Explanation: Colloidal particles acquire a charge due to the selective absorption of ions from the dispersion medium onto their surface. This charge helps in stabilizing the colloidal particles by preventing their aggregation.
78. Which of the following is a method for preparing colloids by dispersion?
- a) Peptization
- b) Condensation
- c) Coagulation
- d) Ultrafiltration
Answer: a) Peptization
Explanation: Peptization is a method of preparing colloids by dispersion. In this process, a precipitate is converted into a colloid by shaking it with a small amount of electrolyte.
79. An example of a solid dispersed in a gas is:
- a) Fog
- b) Smoke
- c) Foam
- d) Emulsion
Answer: b) Smoke
Explanation: Smoke is a colloidal system where solid particles are dispersed in a gas (air). It is an example of a solid-in-gas colloidal system.
80. Which of the following colloids shows a positive charge on its particles?
- a) Gold sol
- b) Ferric hydroxide sol
- c) Arsenic sulphide sol
- d) Starch sol
Answer: b) Ferric hydroxide sol
Explanation: Ferric hydroxide sol is positively charged because it absorbs Fe³⁺ ions from the dispersion medium onto its surface. This gives the colloidal particles a positive charge.
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