Here below some basic MCQ’s about “Colloids and Emulsions” with answer explanation for practice and exam preparation. Let’s check one by one.
1. Which of the following is an example of a colloidal solution?
- a) Sugar solution
- b) Salt solution
- c) Milk
- d) Glucose solution
Answer: c) Milk
Explanation: Milk is an example of a colloidal solution, specifically an emulsion, where liquid fat globules are dispersed in water. In contrast, sugar, salt, and glucose solutions are true solutions, not colloids.
2. The dispersed phase in a colloidal solution of smoke is:
- a) Solid
- b) Liquid
- c) Gas
- d) Plasma
Answer: a) Solid
Explanation: Smoke is an example of a solid dispersed in a gas. The solid particles (soot, ash) are suspended in the gas (air).
3. Which of the following is an example of a lyophilic colloid?
- a) Starch
- b) Ferric hydroxide
- c) Gold sol
- d) Sulphur sol
Answer: a) Starch
Explanation: Lyophilic colloids are colloids that have an affinity for the solvent, meaning they are easily formed. Starch is a lyophilic colloid because it can readily form a colloidal solution in water. Ferric hydroxide, gold sol, and sulphur sol are examples of lyophobic colloids, which have little affinity for the solvent and are less stable.
4. Which one of the following methods is not suitable for the purification of colloidal solutions?
- a) Dialysis
- b) Ultrafiltration
- c) Electrophoresis
- d) Cottrell precipitator
Answer: d) Cottrell precipitator
Explanation: The Cottrell precipitator is used to remove smoke particles from industrial gases and is not used for the purification of colloidal solutions. Dialysis, ultrafiltration, and electrophoresis are suitable methods for the purification of colloids.
5. Tyndall effect is observed in:
- a) True solutions
- b) Suspensions
- c) Colloidal solutions
- d) Both true solutions and colloidal solutions
Answer: c) Colloidal solutions
Explanation: The Tyndall effect is the scattering of light by colloidal particles when light passes through a colloidal solution. True solutions do not show the Tyndall effect, as the particles are too small to scatter light. Suspensions may scatter light, but they are not stable systems like colloids.
6. An emulsion is a colloidal system in which:
- a) Gas is dispersed in liquid
- b) Liquid is dispersed in another liquid
- c) Solid is dispersed in gas
- d) Solid is dispersed in liquid
Answer: b) Liquid is dispersed in another liquid
Explanation: An emulsion is a colloidal system where tiny droplets of one liquid are dispersed in another liquid with which it is immiscible. For example, milk is an emulsion where fat is dispersed in water.
7. Which of the following stabilizes an emulsion?
- a) Surfactants
- b) Electrolytes
- c) Alcohol
- d) None of the above
Answer: a) Surfactants
Explanation: Surfactants, also known as emulsifying agents, stabilize emulsions by reducing the surface tension between the dispersed phase and the dispersion medium, preventing the droplets from coalescing.
8. Which of the following types of colloids is a gel?
- a) Aerosol
- b) Foam
- c) Sol
- d) Jelly
Answer: d) Jelly
Explanation: A gel is a type of colloid in which the dispersed phase is a solid and the dispersion medium is a liquid. Jelly is a common example of a gel, where a semi-solid structure is formed.
9. Which of the following processes is used to coagulate a colloidal solution?
- a) Addition of electrolytes
- b) Heating
- c) Addition of oppositely charged colloid
- d) All of the above
Answer: d) All of the above
Explanation: Coagulation of a colloidal solution can be brought about by adding electrolytes, heating the solution, or mixing it with an oppositely charged colloid. These processes neutralize the charge on the colloidal particles, leading to aggregation and settling.
10. Gold sol is an example of:
- a) Lyophobic colloid
- b) Lyophilic colloid
- c) Emulsion
- d) Aerosol
Answer: a) Lyophobic colloid
Explanation: Gold sol is a lyophobic colloid, meaning it does not have a strong affinity for the solvent and requires stabilization. Lyophobic colloids are less stable and more difficult to prepare than lyophilic colloids.
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).
21. In a colloidal sol, which of the following forces stabilize the colloidal particles?
- a) Gravitational forces
- b) Electrostatic repulsion
- c) Magnetic forces
- d) van der Waals forces
Answer: b) Electrostatic repulsion
Explanation: Colloidal particles are stabilized primarily by electrostatic repulsion. The particles carry like charges, which prevent them from coming together and aggregating.
22. Which of the following is an example of an aerosol?
- a) Fog
- b) Butter
- c) Rubber
- d) Milk
Answer: a) Fog
Explanation: An aerosol is a colloidal system where a liquid is dispersed in a gas. Fog consists of tiny water droplets dispersed in air, making it an example of an aerosol.
23. The method used to separate colloidal particles from impurities is:
- a) Coagulation
- b) Electrophoresis
- c) Ultrafiltration
- d) Sedimentation
Answer: c) Ultrafiltration
Explanation: Ultrafiltration is a technique used to separate colloidal particles from impurities based on particle size. It employs special filters with very fine pores that allow small impurities to pass through but retain colloidal particles.
24. The process by which a colloidal sol is converted into a gel is known as:
- a) Peptization
- b) Gelation
- c) Coagulation
- d) Electrolysis
Answer: b) Gelation
Explanation: Gelation is the process by which a colloidal sol is converted into a gel. It involves the formation of a three-dimensional network that traps the dispersion medium, giving the colloid a semi-solid structure.
25. Which of the following is true for a lyophilic colloid?
- a) It can be easily precipitated
- b) It has a strong affinity for the dispersion medium
- c) It is unstable
- d) It cannot be easily prepared
Answer: b) It has a strong affinity for the dispersion medium
Explanation: Lyophilic colloids have a strong affinity for the dispersion medium (such as water), making them easy to form and relatively stable compared to lyophobic colloids.
26. When an electrolyte is added to a colloidal sol, the colloidal particles tend to:
- a) Coagulate
- b) Become more stable
- c) Exhibit Brownian motion
- d) Increase in size
Answer: a) Coagulate
Explanation: Adding an electrolyte to a colloidal sol neutralizes the charges on the colloidal particles, causing them to aggregate and settle down as a precipitate, leading to coagulation.
27. The gold number is an indicator of:
- a) The size of colloidal particles
- b) The stability of a colloid
- c) The color of colloidal solutions
- d) The type of colloid formed
Answer: b) The stability of a colloid
Explanation: The gold number indicates the amount of a protective colloid required to prevent the coagulation of a gold sol when an electrolyte is added. A lower gold number indicates a more effective protective colloid, and hence, a more stable colloidal solution.
28. Brownian movement in colloids is due to:
- a) Gravitational forces
- b) Intermolecular collisions
- c) Random collisions of molecules of the dispersion medium with the colloidal particles
- d) Attractive forces between colloidal particles
Answer: c) Random collisions of molecules of the dispersion medium with the colloidal particles
Explanation: Brownian movement is the random, zig-zag motion of colloidal particles due to the continuous bombardment of the particles by the molecules of the dispersion medium.
29. Which of the following will not coagulate a colloidal sol?
- a) Adding a suitable electrolyte
- b) Boiling the sol
- c) Adding an oppositely charged colloid
- d) Cooling the sol
Answer: d) Cooling the sol
Explanation: Coagulation of colloidal sols occurs by adding an electrolyte, heating the sol, or adding an oppositely charged colloid. Cooling a sol does not cause coagulation, as it doesn’t affect the charge or movement of particles significantly.
30. In a colloidal system, the particles of the dispersed phase can be separated by:
- a) Filtration
- b) Centrifugation
- c) Decantation
- d) Evaporation
Answer: b) Centrifugation
Explanation: The particles of the dispersed phase in a colloid are small enough to pass through normal filters but can be separated by centrifugation, a process in which rapid spinning separates particles based on their size and mass.
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.
41. Which of the following is not a method for the purification of colloids?
- a) Dialysis
- b) Electrophoresis
- c) Ultrafiltration
- d) Sublimation
Answer: d) Sublimation
Explanation: Sublimation is a process in which a solid turns into gas without passing through the liquid phase, and it is not used for the purification of colloids. Dialysis, electrophoresis, and ultrafiltration are all methods used for colloid purification.
42. Which of the following is not a characteristic of lyophobic colloids?
- a) They are irreversible
- b) They are stable in the presence of small amounts of electrolytes
- c) They are less stable than lyophilic colloids
- d) They are prepared by dispersion or condensation methods
Answer: b) They are stable in the presence of small amounts of electrolytes
Explanation: Lyophobic colloids are not stable in the presence of even small amounts of electrolytes, as the electrolytes tend to coagulate the colloid. Lyophilic colloids, on the other hand, are more stable in the presence of electrolytes.
43. Which of the following is an example of a colloidal system where the dispersed phase is a liquid and the dispersion medium is a gas?
- a) Emulsion
- b) Foam
- c) Aerosol
- d) Sol
Answer: c) Aerosol
Explanation: An aerosol is a colloidal system where the dispersed phase is a liquid, and the dispersion medium is a gas. Examples include fog and mist, where liquid water droplets are dispersed in air.
44. The formation of micelles occurs when the concentration of soap or detergent exceeds a certain threshold. This threshold is known as:
- a) Critical temperature
- b) Critical micelle concentration
- c) Coagulation point
- d) Peptization limit
Answer: b) Critical micelle concentration
Explanation: Micelles form when the concentration of soap or detergent in a solution exceeds the critical micelle concentration (CMC). Above this concentration, the soap molecules aggregate to form micelles, which help in the cleaning process.
45. Which of the following properties is shown by colloidal solutions but not by true solutions?
- a) Homogeneity
- b) Tyndall effect
- c) No settling of particles
- d) Ability to pass through normal filters
Answer: b) Tyndall effect
Explanation: Colloidal solutions show the Tyndall effect (scattering of light), which is not seen in true solutions because the particles in a true solution are too small to scatter light.
46. Which of the following is used for the purification of colloids by the process of diffusion?
- a) Ultrafiltration
- b) Dialysis
- c) Coagulation
- d) Centrifugation
Answer: b) Dialysis
Explanation: Dialysis is used for the purification of colloidal solutions by allowing the small impurities (ions, molecules) to pass through a semi-permeable membrane, while the larger colloidal particles are retained.
47. The stability of lyophilic sols is due to:
- a) Electric charge on colloidal particles
- b) Absorption of dispersion medium on the surface of colloidal particles
- c) Presence of electrolytes
- d) Peptization
Answer: b) Absorption of dispersion medium on the surface of colloidal particles
Explanation: Lyophilic sols are stable because of the strong affinity between the colloidal particles and the dispersion medium, which leads to the absorption of the medium onto the surface of the particles, preventing coagulation.
48. Which of the following will show maximum coagulating power for a negatively charged sol?
- a) NaCl
- b) BaCl₂
- c) AlCl₃
- d) KCl
Answer: c) AlCl₃
Explanation: According to Hardy-Schulze rule, the coagulating power of an ion increases with its charge. Since Al³⁺ carries a +3 charge, it will have a higher coagulating power for negatively charged sols compared to Na⁺ (+1), K⁺ (+1), and Ba²⁺ (+2).
49. Which of the following techniques is based on the difference in the size of particles for the purification of colloids?
- a) Ultrafiltration
- b) Electrophoresis
- c) Dialysis
- d) Peptization
Answer: a) Ultrafiltration
Explanation: Ultrafiltration is based on the difference in particle size. It involves passing the colloidal solution through filters with very fine pores, allowing smaller impurities to pass through while retaining the colloidal particles.
50. The color of a colloidal solution depends on:
- a) The nature of the dispersed phase only
- b) The size of the colloidal particles
- c) The temperature of the system
- d) The viscosity of the medium
Answer: b) The size of the colloidal particles
Explanation: The color of a colloidal solution depends on the size of the colloidal particles. As the particle size changes, the wavelength of light scattered by the particles also changes, leading to different colors.
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.
61. Which of the following is an example of an oil-in-water emulsion?
- a) Butter
- b) Cold cream
- c) Milk
- d) Hair cream
Answer: c) Milk
Explanation: Milk is an oil-in-water emulsion, where tiny droplets of fat are dispersed in water. Butter and cold cream, on the other hand, are water-in-oil emulsions.
62. Which of the following colloids is classified as a lyophobic colloid?
- a) Starch sol
- b) Protein sol
- c) Sulphur sol
- d) Gelatin
Answer: c) Sulphur sol
Explanation: Lyophobic colloids (solvent-hating) like sulphur sol have little affinity for the dispersion medium and are not stable. They are less stable and require stabilizing agents, unlike lyophilic colloids like starch and protein sols.
63. In which of the following processes is a colloid converted into a sol?
- a) Peptization
- b) Coagulation
- c) Sublimation
- d) Adsorption
Answer: a) Peptization
Explanation: Peptization is the process by which a precipitate is converted into a colloidal sol by adding a small amount of electrolyte, which causes the dispersion of particles into colloidal size.
64. Which of the following factors does not affect the Tyndall effect?
- a) Wavelength of light used
- b) Size of colloidal particles
- c) Concentration of colloidal particles
- d) Nature of the colloid
Answer: d) Nature of the colloid
Explanation: The Tyndall effect depends on the wavelength of light, the size of the colloidal particles, and their concentration. The specific nature of the colloid does not directly affect the scattering of light.
65. Which of the following statements is true for a lyophilic colloid?
- a) They are irreversible
- b) They can be easily coagulated by electrolytes
- c) They show high viscosity
- d) They are unstable in the presence of a small amount of electrolyte
Answer: c) They show high viscosity
Explanation: Lyophilic colloids (solvent-loving) form stable solutions and exhibit high viscosity due to the strong affinity between the colloidal particles and the dispersion medium. They are generally reversible and stable in the presence of electrolytes.
66. Which of the following phenomena is used to distinguish between a colloidal solution and a true solution?
- a) Brownian movement
- b) Tyndall effect
- c) Coagulation
- d) Electrophoresis
Answer: b) Tyndall effect
Explanation: The Tyndall effect, which is the scattering of light by colloidal particles, can be used to distinguish between a colloidal solution and a true solution, as true solutions do not scatter light.
67. Which of the following methods cannot be used for the preparation of colloids?
- a) Peptization
- b) Ultrafiltration
- c) Condensation
- d) Dispersion
Answer: b) Ultrafiltration
Explanation: Ultrafiltration is used for the purification of colloidal solutions, not for their preparation. Colloids can be prepared by peptization, condensation, and dispersion methods.
68. Which of the following is not an example of a colloidal solution?
- a) Soap solution
- b) Sugar solution
- c) Blood
- d) Milk
Answer: b) Sugar solution
Explanation: A sugar solution is a true solution, where the solute (sugar) completely dissolves in the solvent (water). Soap solution, blood, and milk are examples of colloidal solutions.
69. Which of the following methods can be used to destroy the charge on colloidal particles, leading to coagulation?
- a) Adding a protective colloid
- b) Boiling the sol
- c) Decreasing temperature
- d) Addition of more solvent
Answer: b) Boiling the sol
Explanation: Boiling a colloidal solution can reduce the charge on colloidal particles, leading to coagulation. This is because the heat disrupts the stabilization caused by the charge, allowing the particles to aggregate.
70. In the Hardy-Schulze rule, the coagulating power of an ion increases with:
- a) Its size
- b) Its charge
- c) Its solubility
- d) Its molecular weight
Answer: b) Its charge
Explanation: According to the Hardy-Schulze rule, the greater the charge on the ions, the greater their ability to coagulate colloids. Highly charged ions neutralize the charge on colloidal particles more effectively, causing coagulation.
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.
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.
91. Which of the following is true for an oil-in-water emulsion?
- a) Oil is the dispersion medium
- b) Water is the dispersion medium
- c) Water is the dispersed phase
- d) Neither oil nor water is involved
Answer: b) Water is the dispersion medium
Explanation: In an oil-in-water emulsion, oil is the dispersed phase, and water is the dispersion medium. Examples include milk and salad dressings.
92. Which of the following processes can be used to remove dissolved gases from colloidal solutions?
- a) Dialysis
- b) Ultrafiltration
- c) Boiling
- d) Adsorption
Answer: c) Boiling
Explanation: Boiling is used to remove dissolved gases from colloidal solutions. The heat causes the gases to escape from the solution.
93. Which of the following statements is true about the nature of colloidal solutions?
- a) They are always transparent
- b) They are homogeneous in nature
- c) They exhibit both the Tyndall effect and Brownian movement
- d) They do not scatter light
Answer: c) They exhibit both the Tyndall effect and Brownian movement
Explanation: Colloidal solutions exhibit both the Tyndall effect (scattering of light) and Brownian movement (random motion of particles), which are characteristic properties of colloids.
94. Which of the following colloidal systems has a liquid dispersed in a solid?
- a) Gel
- b) Foam
- c) Emulsion
- d) Aerosol
Answer: a) Gel
Explanation: In a gel, a liquid is dispersed in a solid. Examples of gels include jelly and certain cosmetics.
95. Which of the following is true regarding associated colloids?
- a) They are always lyophilic in nature
- b) They exhibit properties of both true solutions and colloidal solutions
- c) They can only exist in solid form
- d) They do not form micelles
Answer: b) They exhibit properties of both true solutions and colloidal solutions
Explanation: Associated colloids, such as soap solutions, exhibit the properties of both true solutions and colloidal solutions. They form micelles at higher concentrations.
96. The phenomenon of adsorption is used in:
- a) Removing gases from liquids
- b) Coagulation of colloidal particles
- c) Purification of colloidal solutions
- d) All of the above
Answer: d) All of the above
Explanation: Adsorption is a phenomenon used in various applications such as removing gases from liquids, coagulating colloidal particles, and purifying colloidal solutions by adsorbing impurities.
97. Which of the following statements is true for electrophoresis?
- a) It is the random movement of colloidal particles
- b) It is the movement of colloidal particles under an electric field
- c) It causes coagulation of colloidal solutions
- d) It does not affect the charge on colloidal particles
Answer: b) It is the movement of colloidal particles under an electric field
Explanation: Electrophoresis is the movement of colloidal particles towards the oppositely charged electrode under the influence of an electric field. It is used to study the charge on colloidal particles.
98. Which of the following is used to coagulate rubber from latex?
- a) Sulphuric acid
- b) Gelatin
- c) Sodium chloride
- d) Calcium chloride
Answer: a) Sulphuric acid
Explanation: Sulphuric acid is used to coagulate rubber from latex. The acid neutralizes the charge on the rubber particles, causing them to aggregate and form a solid mass of rubber.
99. Which of the following is an example of a colloidal system in which a gas is dispersed in a solid?
- a) Aerosol
- b) Gel
- c) Foam
- d) Solid foam
Answer: d) Solid foam
Explanation: Solid foam is a colloidal system where gas is dispersed in a solid. Examples include foam rubber and pumice stone.
100. Which of the following best describes coagulation?
- a) The breaking up of a colloidal solution into smaller particles
- b) The formation of colloidal particles from a true solution
- c) The process of settling of colloidal particles after neutralization of charge
- d) The continuous scattering of light in a colloidal solution
Answer: c) The process of settling of colloidal particles after neutralization of charge
Explanation: Coagulation is the process where colloidal particles settle down after their charge has been neutralized, usually by the addition of an electrolyte.
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