31. Which of the following is a protective colloid?
- a) Ferric hydroxide sol
- b) Starch
- c) Copper sol
- d) Sulphur sol
Answer: b) Starch
Explanation: A protective colloid is a substance that stabilizes another colloid and prevents it from coagulating. Starch acts as a protective colloid by preventing the coagulation of colloidal particles when electrolytes are added.
32. Which one of the following properties is not exhibited by colloidal solutions?
- a) Coagulation
- b) Tyndall effect
- c) Electrophoresis
- d) Crystallization
Answer: d) Crystallization
Explanation: Colloidal solutions do not exhibit crystallization, as the particles are dispersed in the medium and are too small to form crystals. Coagulation, Tyndall effect, and electrophoresis are typical properties of colloidal solutions.
33. Which type of colloidal system is blood?
- a) Sol
- b) Gel
- c) Aerosol
- d) Foam
Answer: a) Sol
Explanation: Blood is a colloidal system in which solid particles (like proteins, cells) are dispersed in a liquid medium (plasma). This makes blood a sol.
34. What happens to the stability of a colloidal solution if an electrolyte is added in excess?
- a) Stability increases
- b) Stability remains the same
- c) Stability decreases, and coagulation occurs
- d) Nothing happens
Answer: c) Stability decreases, and coagulation occurs
Explanation: When an electrolyte is added in excess, it neutralizes the charge on the colloidal particles, leading to coagulation. This decreases the stability of the colloid.
35. The separation of colloidal particles from impurities by diffusion through a semi-permeable membrane is called:
- a) Dialysis
- b) Ultrafiltration
- c) Peptization
- d) Electrophoresis
Answer: a) Dialysis
Explanation: Dialysis is the process of separating colloidal particles from smaller ions or impurities by using a semi-permeable membrane. This allows the impurities to pass through the membrane while retaining the colloidal particles.
36. The addition of alum to water purifies it by:
- a) Coagulation of colloidal impurities
- b) Sedimentation of impurities
- c) Forming a protective layer
- d) Reducing water hardness
Answer: a) Coagulation of colloidal impurities
Explanation: Alum is added to water to coagulate colloidal impurities, such as clay and organic matter. It neutralizes the charges on the colloidal particles, causing them to aggregate and settle down, thus purifying the water.
37. Which of the following is an example of a multimolecular colloid?
- a) Ferric hydroxide sol
- b) Gold sol
- c) Protein
- d) Starch
Answer: b) Gold sol
Explanation: In a multimolecular colloid, a large number of small molecules aggregate to form particles of colloidal size. Gold sol is an example of a multimolecular colloid, where small gold atoms aggregate to form colloidal particles.
38. The process of converting a precipitate into a colloidal solution by shaking it with an electrolyte is called:
- a) Peptization
- b) Coagulation
- c) Dialysis
- d) Electrophoresis
Answer: a) Peptization
Explanation: Peptization is the process in which a precipitate is converted into a colloidal solution by adding a small amount of an electrolyte. The electrolyte helps to disperse the precipitate into colloidal-sized particles.
39. Which of the following is a lyophobic colloid?
- a) Gelatin
- b) Starch
- c) Sulphur sol
- d) Rubber
Answer: c) Sulphur sol
Explanation: Lyophobic colloids are colloidal systems where the dispersed phase has little affinity for the dispersion medium. Sulphur sol is an example of a lyophobic colloid, which is not easily formed and is less stable compared to lyophilic colloids like gelatin and starch.
40. The Brownian motion is more prominent in:
- a) Larger colloidal particles
- b) Smaller colloidal particles
- c) Suspensions
- d) True solutions
Answer: b) Smaller colloidal particles
Explanation: Brownian motion is more prominent in smaller colloidal particles because the random collisions with the molecules of the dispersion medium have a greater effect on the motion of smaller particles.
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