MCQs on Surface Chemistry – CBSE Class 12 NCERT

Physical Chemistry – MCQ Titles (NCERT Based)
Course: CBSE Class 12 Chemistry – MCQs with Answers and Explanations

The following 50 NCERT-based MCQs are structured strictly according to the CBSE Class 12 Chemistry chapter “Surface Chemistry”. The questions are section-wise and designed to strengthen conceptual clarity, definitions, applications, and exam-oriented understanding, making them ideal for CBSE board exam preparation.

Section A: Basic Concepts of Surface Chemistry

1. Surface chemistry deals with:

A. Bulk properties of substances
B. Chemical reactions in solution
C. Phenomena occurring at surfaces or interfaces
D. Nuclear reactions

Correct Answer: C
Explanation: Surface chemistry studies physical and chemical phenomena occurring at interfaces.

2. Adsorption is:

A. Absorption of gas into liquid
B. Accumulation of substance on surface
C. Dissolution of solid
D. Diffusion of molecules

Correct Answer: B
Explanation: Adsorption is a surface phenomenon where molecules accumulate on a surface.

3. Which of the following is a surface phenomenon?

A. Diffusion
B. Adsorption
C. Osmosis
D. Crystallization

Correct Answer: B
Explanation: Adsorption occurs only at the surface.

4. The substance adsorbed on a surface is called:

A. Adsorbent
B. Adsorbate
C. Solvent
D. Catalyst

Correct Answer: B
Explanation: Adsorbate is the substance that gets adsorbed.

5. The material on whose surface adsorption occurs is:

A. Adsorbate
B. Catalyst
C. Adsorbent
D. Colloid

Correct Answer: C
Explanation: Adsorbent provides the surface for adsorption.

Section B: Types of Adsorption

6. Which adsorption involves weak van der Waals forces?

A. Chemisorption
B. Physical adsorption
C. Absorption
D. Catalysis

Correct Answer: B
Explanation: Physical adsorption (physisorption) involves weak forces.

7. Chemisorption is:

A. Reversible
B. Multilayered
C. Involves chemical bond formation
D. Independent of temperature

Correct Answer: C
Explanation: Chemisorption involves formation of chemical bonds.

8. Which type of adsorption increases with temperature?

A. Physical adsorption
B. Chemisorption
C. Absorption
D. Desorption

Correct Answer: B
Explanation: Chemisorption requires activation energy.

9. Physisorption is favoured by:

A. High temperature
B. Low pressure
C. Low temperature
D. Chemical bonding

Correct Answer: C
Explanation: Lower temperature stabilizes weak intermolecular forces.

10. Chemisorption is usually:

A. Multilayered
B. Reversible
C. Monolayered
D. Weak

Correct Answer: C
Explanation: Chemisorption forms a single layer on the surface.

Section C: Adsorption Isotherms

11. Adsorption isotherm represents relation between:

A. Pressure and temperature
B. Amount adsorbed and pressure
C. Volume and temperature
D. Surface area and pressure

Correct Answer: B
Explanation: It shows adsorption at constant temperature.

12. Freundlich adsorption isotherm is:

A. Exact
B. Theoretical
C. Empirical
D. Mathematical

Correct Answer: C
Explanation: Freundlich isotherm is based on experimental data.

13. Freundlich equation is:

A. x/m = kP
B. x/m = kP¹⁄ⁿ
C. x/m = KP
D. x/m = nP

Correct Answer: B
Explanation: It relates amount adsorbed to pressure.

14. Freundlich isotherm fails at:

A. Low pressure
B. Moderate pressure
C. High pressure
D. Room temperature

Correct Answer: C
Explanation: At high pressure, adsorption reaches saturation.

15. Langmuir adsorption isotherm assumes:

A. Multilayer adsorption
B. Uniform surface
C. Weak forces
D. Reversible only

Correct Answer: B
Explanation: Langmuir assumed uniform adsorption sites.

Section D: Factors Affecting Adsorption

16. Adsorption increases with:

A. Increase in temperature
B. Decrease in surface area
C. Increase in surface area
D. Increase in volume

Correct Answer: C
Explanation: Larger surface area provides more adsorption sites.

17. Which gas is adsorbed most easily?

A. H₂
B. N₂
C. CO₂
D. He

Correct Answer: C
Explanation: Easily liquefiable gases show higher adsorption.

18. Adsorption decreases with:

A. Increase in pressure
B. Increase in temperature (physisorption)
C. Increase in surface area
D. Increase in mass

Correct Answer: B
Explanation: Physical adsorption is exothermic.

19. Finely divided metals show:

A. Less adsorption
B. More adsorption
C. No adsorption
D. Chemical absorption

Correct Answer: B
Explanation: Finely divided form has high surface area.

20. Activated charcoal is effective due to:

A. High density
B. Porous nature
C. Chemical bonding
D. Low surface area

Correct Answer: B
Explanation: Porosity increases surface area.

Section E: Catalysis

21. Catalyst works by:

A. Increasing activation energy
B. Changing equilibrium constant
C. Lowering activation energy
D. Increasing temperature

Correct Answer: C
Explanation: Catalyst provides alternate low-energy pathway.

22. Homogeneous catalyst exists in:

A. Same phase as reactants
B. Solid phase
C. Different phase
D. Gaseous phase only

Correct Answer: A
Explanation: Homogeneous catalysts are in same phase.

23. Which is a heterogeneous catalyst?

A. H⁺ ions
B. Enzyme
C. Fe in Haber process
D. Acid catalyst

Correct Answer: C
Explanation: Iron is solid while reactants are gases.

24. Promoters are substances that:

A. Increase catalyst amount
B. Reduce catalyst efficiency
C. Enhance catalyst activity
D. Replace catalyst

Correct Answer: C
Explanation: Promoters increase effectiveness of catalysts.

25. Poisoning of catalyst refers to:

A. Catalyst activation
B. Reduction in catalyst activity
C. Increase in surface area
D. Catalyst regeneration

Correct Answer: B
Explanation: Impurities block active sites.

Section F: Colloids

26. Colloids are:

A. Homogeneous mixtures
B. Heterogeneous mixtures
C. True solutions
D. Pure substances

Correct Answer: B
Explanation: Colloids are heterogeneous but appear homogeneous.

27. Size of colloidal particles lies between:

A. < 1 nm
B. 1–100 nm
C. > 1000 nm
D. Exactly 100 nm

Correct Answer: B
Explanation: Intermediate particle size defines colloids.

28. Dispersed phase is:

A. Medium
B. Solvent
C. Colloidal particles
D. Adsorbent

Correct Answer: C
Explanation: Dispersed phase forms the colloidal particles.

29. Milk is an example of:

A. Solid sol
B. Foam
C. Emulsion
D. Aerosol

Correct Answer: C
Explanation: Liquid in liquid system.

30. Tyndall effect is:

A. Scattering of light by colloids
B. Reflection of light
C. Absorption of light
D. Diffusion of light

Correct Answer: A
Explanation: It distinguishes colloids from true solutions.

Section G: Properties of Colloids

31. Brownian motion is due to:

A. Gravity
B. Electric field
C. Random movement of particles
D. Magnetic field

Correct Answer: C
Explanation: It results from collisions with molecules of medium.

32. Zeta potential is related to:

A. Surface tension
B. Electrical charge
C. Viscosity
D. Density

Correct Answer: B
Explanation: It represents charge on colloidal particles.

33. Coagulation of colloids means:

A. Dispersion
B. Precipitation
C. Emulsification
D. Stabilization

Correct Answer: B
Explanation: Particles aggregate and settle.

34. Hardy–Schulze rule states:

A. Smaller ion is effective
B. Higher charge ion causes faster coagulation
C. Neutral ions are effective
D. Temperature dependent

Correct Answer: B
Explanation: Coagulating power increases with valency.

35. Which electrolyte coagulates negatively charged sol?

A. NaCl
B. KCl
C. AlCl₃
D. HCl

Correct Answer: C
Explanation: Al³⁺ has highest coagulating power.

Section H: Applications and Exam-Oriented MCQs

36. Which is a lyophilic colloid?

A. Gold sol
B. Starch sol
C. Sulphur sol
D. Arsenic sulphide

Correct Answer: B
Explanation: Lyophilic sols have strong affinity for solvent.

37. Which sol is reversible?

A. Lyophobic
B. Metallic sol
C. Lyophilic
D. Aerosol

Correct Answer: C
Explanation: Lyophilic sols can be easily reformed.

38. Emulsifier helps in:

A. Coagulation
B. Stabilizing emulsions
C. Precipitation
D. Adsorption

Correct Answer: B
Explanation: Emulsifier prevents separation.

39. Which is an aerosol?

A. Smoke
B. Milk
C. Paint
D. Jelly

Correct Answer: A
Explanation: Solid in gas system.

40. Fog is an example of:

A. Solid sol
B. Liquid aerosol
C. Foam
D. Emulsion

Correct Answer: B
Explanation: Liquid droplets dispersed in gas.

41. Surface chemistry plays important role in:

A. Electrochemistry
B. Catalysis
C. Thermodynamics
D. Nuclear chemistry

Correct Answer: B
Explanation: Catalysis depends on surface adsorption.

42. Which catalyst is used in Contact process?

A. Iron
B. Nickel
C. Vanadium pentoxide
D. Platinum

Correct Answer: C
Explanation: V₂O₅ catalyzes SO₂ oxidation.

43. Adsorption is generally:

A. Endothermic
B. Exothermic
C. Neutral
D. Explosive

Correct Answer: B
Explanation: Adsorption releases heat.

44. Which property helps detect colloids?

A. Osmosis
B. Diffusion
C. Tyndall effect
D. Dialysis

Correct Answer: C
Explanation: Light scattering indicates colloids.

45. Which method purifies colloids?

A. Distillation
B. Crystallization
C. Dialysis
D. Filtration

Correct Answer: C
Explanation: Dialysis removes dissolved impurities.

46. Gold sol is prepared by:

A. Adsorption
B. Reduction method
C. Oxidation
D. Precipitation

Correct Answer: B
Explanation: Reduction of gold salts produces sol.

47. Shape of colloidal particles can be:

A. Only spherical
B. Irregular
C. Spherical or irregular
D. Cubical only

Correct Answer: C
Explanation: Shape varies with substance.

48. Which is not a colloidal system?

A. Smoke
B. Milk
C. Sugar solution
D. Paint

Correct Answer: C
Explanation: Sugar solution is a true solution.

49. Adsorption is used in:

A. Dehumidifiers
B. Water purification
C. Gas masks
D. All of these

Correct Answer: D
Explanation: Adsorption has wide industrial applications.

50. Surface chemistry mainly studies:

A. Bulk reactions
B. Nuclear changes
C. Surface phenomena
D. Acid-base reactions

Correct Answer: C
Explanation: Focus is on interfacial phenomena.

✅ End of NCERT-Based MCQs on Surface Chemistry – Class 12 Chemistry