Q.1 Which of the following is a heterogeneous catalyst?
Pt in H2 + O2 reaction
Enzymes in biological reactions
Acetic acid in esterification
H2SO4 in dehydration of alcohols
Explanation - Heterogeneous catalysts are in a different phase than the reactants. Platinum (Pt) is solid while H2 and O2 are gases.
Correct answer is: Pt in H2 + O2 reaction
Q.2 What is the main mechanism of adsorption of gases on solids?
Physical adsorption
Chemical adsorption
Capillary condensation
Surface tension
Explanation - Adsorption involves accumulation of molecules on the surface, mainly through van der Waals forces in physical adsorption.
Correct answer is: Physical adsorption
Q.3 Which of the following factors does NOT affect adsorption?
Surface area of adsorbent
Pressure of adsorbate gas
Nature of adsorbent
Color of adsorbent
Explanation - Adsorption depends on surface area, pressure, temperature, and chemical nature of adsorbent; color has no effect.
Correct answer is: Color of adsorbent
Q.4 Which of the following is an example of chemisorption?
H2 adsorbed on Pt
N2 on charcoal
CO2 on silica gel
O2 on activated carbon
Explanation - Chemisorption involves chemical bond formation. Hydrogen forms bonds with platinum surface atoms.
Correct answer is: H2 adsorbed on Pt
Q.5 The decrease in adsorption with increase in temperature is characteristic of:
Chemisorption
Physisorption
Catalysis
Colloids
Explanation - Physisorption is exothermic and weaker; higher temperatures provide energy for molecules to desorb.
Correct answer is: Physisorption
Q.6 Which of the following best describes a colloid?
Homogeneous mixture
Heterogeneous mixture with particle size 1-100 nm
Pure compound
Suspension with particle size >1 μm
Explanation - Colloids have dispersed particles in the nanometer range, which do not settle on standing.
Correct answer is: Heterogeneous mixture with particle size 1-100 nm
Q.7 What is the Tyndall effect?
Diffusion of gases
Scattering of light by colloidal particles
Boiling point elevation
Catalyst action
Explanation - Colloidal particles scatter light, making a beam visible, which is the Tyndall effect.
Correct answer is: Scattering of light by colloidal particles
Q.8 Which of the following pairs is correctly matched?
Lyophilic sol – hydrophobic solvent
Lyophobic sol – water
Hydrosol – water as dispersion medium
Aerosol – solid in solid dispersion
Explanation - Hydrosols are colloids where water is the dispersion medium.
Correct answer is: Hydrosol – water as dispersion medium
Q.9 Which of the following is used as a protective colloid?
Gelatin
Aluminium chloride
Acetic acid
Ferric oxide
Explanation - Protective colloids stabilize lyophobic sols by forming a protective layer around the particles.
Correct answer is: Gelatin
Q.10 In adsorption, which adsorption isotherm represents a logarithmic relationship between amount adsorbed and pressure?
Freundlich isotherm
Langmuir isotherm
BET isotherm
Henry's law
Explanation - Freundlich isotherm: x/m = kP^(1/n), representing adsorption on heterogeneous surfaces.
Correct answer is: Freundlich isotherm
Q.11 Which of the following is true for Langmuir adsorption isotherm?
Applicable for multilayer adsorption
Assumes uniform surface and monolayer coverage
Independent of temperature
Applies to gases in solution
Explanation - Langmuir isotherm models adsorption on a homogeneous surface forming a monolayer.
Correct answer is: Assumes uniform surface and monolayer coverage
Q.12 Which of the following is used in the purification of water by coagulation?
Alum
NaCl
HCl
KOH
Explanation - Alum causes coagulation of colloidal particles in water, facilitating their removal.
Correct answer is: Alum
Q.13 The phenomenon in which the colloidal solution of a sol settles upon standing is called:
Flocculation
Coagulation
Ostwald ripening
Brownian motion
Explanation - Coagulation is the process of aggregation of colloidal particles leading to settling.
Correct answer is: Coagulation
Q.14 Which of the following is an example of a hydrophobic sol?
As2S3 in water
Gelatin in water
Starch in water
Fe(OH)3 in water
Explanation - Hydrophobic sols are insoluble in water and require stabilizers; As2S3 is one example.
Correct answer is: As2S3 in water
Q.15 Brownian movement of colloidal particles is due to:
Gravity
Molecular bombardment of dispersion medium
Magnetic field
Surface tension
Explanation - The constant motion of colloidal particles results from collisions with molecules of the dispersion medium.
Correct answer is: Molecular bombardment of dispersion medium
Q.16 Which of the following is a practical application of adsorption?
Purification of air using activated charcoal
Gel formation by gelatin
Suspension formation
Emulsion stabilization
Explanation - Activated charcoal adsorbs harmful gases and odors, purifying air or water.
Correct answer is: Purification of air using activated charcoal
Q.17 Micelles are formed in which type of solution?
Electrolyte solutions
Colloidal solutions
Surfactant solutions above CMC
Suspensions
Explanation - Micelles form when surfactant concentration exceeds the critical micelle concentration (CMC).
Correct answer is: Surfactant solutions above CMC
Q.18 Which of the following is an example of an emulsion?
Milk
Air in water
Iodine in alcohol
Sodium chloride in water
Explanation - An emulsion is a colloid where both dispersed phase and dispersion medium are liquids; milk is an example.
Correct answer is: Milk
Q.19 Which of the following is used as a catalyst in the Haber process?
Fe
Ni
Pt
Zn
Explanation - Iron acts as a heterogeneous catalyst in ammonia synthesis from N2 and H2.
Correct answer is: Fe
Q.20 The process of removing colloidal particles using dialysis is called:
Coagulation
Dialysis
Electrophoresis
Ostwald ripening
Explanation - Dialysis separates colloidal particles from ions and small molecules through a semipermeable membrane.
Correct answer is: Dialysis
Q.21 Which of the following is used as a desiccant?
Conc. H2SO4
NaCl
Sugar
MgSO4·7H2O
Explanation - Concentrated sulfuric acid absorbs water and is used as a drying agent or desiccant.
Correct answer is: Conc. H2SO4
Q.22 Which of the following statements is true for chemisorption?
It decreases with temperature
It is reversible
It involves weak van der Waals forces
It is independent of chemical nature of surface
Explanation - Chemisorption usually increases with temperature initially, but excessive heat may break bonds, reducing adsorption.
Correct answer is: It decreases with temperature
Q.23 The surface area of adsorbent per unit mass is maximum for:
Activated charcoal
Graphite
Silica gel
Aluminium oxide
Explanation - Activated charcoal has a highly porous structure providing a very large surface area for adsorption.
Correct answer is: Activated charcoal
Q.24 In which of the following processes adsorption is utilized industrially?
Haber process
Purification of gases
Ostwald process
Contact process
Explanation - Adsorption is widely used to remove impurities or pollutants from gases, e.g., activated charcoal in gas masks.
Correct answer is: Purification of gases