11. Which of the following statements is true about colloids?
- a) Colloidal particles can be seen with a naked eye
- b) Colloidal particles are larger than true solution particles but smaller than suspension particles
- c) Colloidal particles settle down upon standing
- d) Colloidal particles cannot be filtered
Answer: b) Colloidal particles are larger than true solution particles but smaller than suspension particles
Explanation: Colloidal particles are intermediate in size between the small particles in a true solution and the large particles in a suspension. They are too small to be seen with a naked eye, and they do not settle down upon standing.
12. Which of the following is an example of a macromolecular colloid?
- a) Gelatin
- b) Starch
- c) Soap solution
- d) Milk
Answer: a) Gelatin
Explanation: Macromolecular colloids consist of large molecules, such as proteins. Gelatin is a good example of a macromolecular colloid, where the protein molecules form a colloidal solution in water.
13. Which of the following is not a property of colloids?
- a) They scatter light
- b) They show Brownian movement
- c) They exhibit the Tyndall effect
- d) They are homogeneous systems
Answer: d) They are homogeneous systems
Explanation: Colloids are heterogeneous mixtures, not homogeneous systems. The dispersed phase and dispersion medium are distinguishable, even though they are finely divided. They do show the Tyndall effect and Brownian movement.
14. The movement of colloidal particles under the influence of an electric field is called:
- a) Dialysis
- b) Peptization
- c) Electrophoresis
- d) Coagulation
Answer: c) Electrophoresis
Explanation: Electrophoresis is the movement of colloidal particles under the influence of an electric field. The charged particles move towards the oppositely charged electrode.
15. Which of the following will act as the best emulsifying agent?
- a) NaCl
- b) MgCl₂
- c) C₂H₅OH
- d) Soap
Answer: d) Soap
Explanation: Soap acts as an excellent emulsifying agent because it contains both hydrophobic and hydrophilic groups. It reduces the surface tension between oil and water, stabilizing emulsions.
16. A sol in which the dispersion medium is water is called:
- a) Hydrosol
- b) Aerosol
- c) Alcosol
- d) Benzosol
Answer: a) Hydrosol
Explanation: A colloidal solution where water acts as the dispersion medium is called a hydrosol. Examples include starch in water or proteins in water.
17. Which of the following colloidal solutions can show a negative Tyndall effect?
- a) Dilute milk
- b) Sulphur sol
- c) Ferric hydroxide sol
- d) True sugar solution
Answer: d) True sugar solution
Explanation: True solutions like sugar solution do not exhibit the Tyndall effect because the particles are too small to scatter light. Colloidal solutions like milk, sulphur sol, and ferric hydroxide sol exhibit the Tyndall effect.
18. The scattering of light by colloidal particles is called:
- a) Electrophoresis
- b) Tyndall effect
- c) Coagulation
- d) Peptization
Answer: b) Tyndall effect
Explanation: The Tyndall effect is the phenomenon where light is scattered by colloidal particles when it passes through a colloidal dispersion. This is why colloidal solutions appear turbid when viewed at an angle.
19. A colloidal system where the dispersed phase is a gas and the dispersion medium is a liquid is called:
- a) Foam
- b) Emulsion
- c) Sol
- d) Gel
Answer: a) Foam
Explanation: Foam is a type of colloidal system where a gas is dispersed in a liquid. Shaving cream and whipped cream are examples of foams.
20. Which of the following methods can be used to prepare colloidal solutions?
- a) Condensation method
- b) Dispersion method
- c) Peptization
- d) All of the above
Answer: d) All of the above
Explanation: Colloidal solutions can be prepared by condensation methods (where small molecules aggregate into colloidal particles), dispersion methods (where larger particles are broken down), and peptization (the process of converting a precipitate into a colloid by adding an electrolyte).
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