Competency Based MCQs – Class 11 Chemistry NCERT
Competency Based MCQs – Class 11 Chemistry (NCERT Aligned)
Course: CBSE Class 11 Chemistry – MCQs with Answers and Explanations
Section: Exam-Oriented & Practice-Based Titles
The following 50 Competency-Based Multiple Choice Questions (MCQs) are strictly prepared as per the NCERT Class 11 Chemistry syllabus and the latest CBSE assessment focus on application, analysis, and reasoning. These MCQs assess conceptual understanding, real-life application, and problem-solving skills, making them ideal for CBSE board exams and school-based assessments.
Section A: Some Basic Concepts & Mole Concept
1. A student weighs 11 g of CO₂. How many moles of CO₂ are present?
A. 0.25
B. 0.5
C. 1
D. 2
Answer: B
Explanation: Moles = mass ÷ molar mass = 11 ÷ 44 = 0.25 (correct option B after recalculation correction: 11/44 = 0.25).
✔ Corrected: Option A (0.25)
2. Which factor directly affects the molarity of a solution when temperature changes?
A. Mass of solute
B. Number of moles
C. Volume of solution
D. Mole fraction
Answer: C
Explanation: Volume changes with temperature, affecting molarity.
3. A limiting reagent in a reaction is one that
A. has maximum mass
B. reacts fastest
C. is completely consumed
D. remains unreacted
Answer: C
Explanation: It limits the amount of product formed.
4. Mole fraction is preferred in thermodynamic calculations because it is
A. easy to calculate
B. temperature dependent
C. dimensionless
D. mass based
Answer: C
Explanation: Mole fraction does not change with temperature.
5. Empirical formula represents
A. actual number of atoms
B. simplest ratio of atoms
C. molecular mass
D. number of bonds
Answer: B
Explanation: It gives the simplest whole-number ratio.
Section B: Structure of Atom
6. Discrete lines in hydrogen spectrum indicate
A. random electron motion
B. continuous energy levels
C. quantised energy levels
D. nuclear transitions
Answer: C
Explanation: Energy levels are quantised.
7. Which principle explains maximum two electrons in an orbital?
A. Hund’s rule
B. Aufbau principle
C. Pauli exclusion principle
D. Heisenberg uncertainty principle
Answer: C
Explanation: No two electrons can have identical quantum numbers.
8. The orbital with dumbbell shape is
A. s-orbital
B. p-orbital
C. d-orbital
D. f-orbital
Answer: B
Explanation: p-orbitals have dumbbell shape.
9. Which transition releases maximum energy?
A. n = 2 → 1
B. n = 3 → 2
C. n = 4 → 3
D. n = 5 → 4
Answer: A
Explanation: Greater energy gap gives higher energy release.
10. Aufbau principle is based on
A. energy ordering of orbitals
B. electron pairing
C. orbital shape
D. nuclear charge
Answer: A
Explanation: Electrons fill lowest energy orbitals first.
Section C: Periodicity and Chemical Bonding
11. Atomic radius decreases across a period mainly due to
A. increased shielding
B. increased nuclear charge
C. decreased electrons
D. increased mass
Answer: B
Explanation: Nuclear charge increases while shells remain same.
12. Which element has highest electronegativity?
A. Oxygen
B. Nitrogen
C. Chlorine
D. Fluorine
Answer: D
Explanation: Fluorine has smallest size and highest effective nuclear charge.
13. VSEPR theory predicts molecular shape based on
A. bond length
B. bond strength
C. electron pair repulsion
D. orbital overlap
Answer: C
Explanation: Shape minimises electron pair repulsion.
14. Hybridisation of carbon in ethyne is
A. sp³
B. sp²
C. sp
D. dsp²
Answer: C
Explanation: Triple bond involves sp hybridisation.
15. Lone pair causes greater repulsion because it
A. has less charge
B. occupies more space
C. forms pi bonds
D. has lower energy
Answer: B
Explanation: Lone pairs are closer to nucleus.
Section D: States of Matter & Thermodynamics
16. Real gases deviate from ideal behaviour at
A. high temperature, low pressure
B. low temperature, high pressure
C. normal conditions
D. STP only
Answer: B
Explanation: Intermolecular forces become significant.
17. First law of thermodynamics is a statement of
A. entropy
B. spontaneity
C. conservation of energy
D. equilibrium
Answer: C
Explanation: Energy cannot be created or destroyed.
18. Enthalpy change is positive for
A. exothermic reaction
B. endothermic reaction
C. neutral reaction
D. spontaneous reaction
Answer: B
Explanation: Heat is absorbed.
19. Which quantity is a state function?
A. Work
B. Heat
C. Enthalpy
D. Path length
Answer: C
Explanation: State functions depend only on state.
20. Increase in entropy means
A. decrease in randomness
B. no disorder
C. increase in disorder
D. decrease in energy
Answer: C
Explanation: Entropy measures randomness.
Section E: Equilibrium and Redox Reactions
21. Chemical equilibrium is dynamic because
A. reaction stops
B. concentrations change
C. forward and backward reactions continue
D. energy is zero
Answer: C
Explanation: Both reactions occur at equal rates.
22. For an exothermic reaction, increase in temperature
A. increases yield
B. decreases yield
C. no effect
D. stops reaction
Answer: B
Explanation: Equilibrium shifts backward.
23. Oxidation is defined as
A. gain of electrons
B. loss of electrons
C. gain of neutrons
D. loss of protons
Answer: B
Explanation: Oxidation involves electron loss.
24. An oxidising agent
A. loses electrons
B. gains electrons
C. remains unchanged
D. donates protons
Answer: B
Explanation: It gets reduced.
25. Zinc acts as reducing agent because it
A. gains electrons
B. loses electrons
C. is inert
D. forms ions only
Answer: B
Explanation: Zinc loses electrons.
Section F: s-Block and p-Block Elements
26. Alkali metals are highly reactive due to
A. high electronegativity
B. low ionisation enthalpy
C. high melting point
D. small size
Answer: B
Explanation: They lose electrons easily.
27. Lithium shows anomalous behaviour due to
A. large atomic size
B. diagonal relationship
C. high metallic nature
D. inert pair effect
Answer: B
Explanation: Similarity with magnesium.
28. Boron compounds are covalent because boron
A. is metallic
B. has high ionisation enthalpy
C. has large size
D. is electropositive
Answer: B
Explanation: B³⁺ formation is difficult.
29. Carbon shows maximum catenation because
A. it is light
B. it forms ionic bonds
C. C–C bond is strong
D. it has d-orbitals
Answer: C
Explanation: Strong C–C bonds.
30. CO₂ is acidic because it
A. contains hydrogen
B. forms carbonic acid in water
C. has double bonds
D. is gaseous
Answer: B
Explanation: Acidic oxide.
Section G: Organic Chemistry Basics
31. Organic chemistry mainly deals with
A. metals
B. carbon compounds
C. salts
D. acids only
Answer: B
Explanation: Carbon forms vast compounds.
32. Members of homologous series have same
A. molecular mass
B. physical properties
C. functional group
D. boiling point
Answer: C
Explanation: Functional group remains same.
33. IUPAC nomenclature ensures
A. short names
B. systematic naming
C. trivial names
D. local names
Answer: B
Explanation: Avoids ambiguity.
34. Alkenes undergo addition reactions due to
A. sigma bond
B. pi bond
C. ionic bond
D. hydrogen bond
Answer: B
Explanation: Pi bond is weaker.
35. Hybridisation of carbon in methane is
A. sp
B. sp²
C. sp³
D. dsp²
Answer: C
Explanation: Tetrahedral geometry.
Section H: Environmental & Everyday Chemistry
36. Ozone depletion is mainly caused by
A. CO₂
B. SO₂
C. CFCs
D. NO₂
Answer: C
Explanation: Chlorine radicals destroy ozone.
37. Greenhouse gas responsible for global warming is
A. O₂
B. N₂
C. CO₂
D. He
Answer: C
Explanation: CO₂ traps heat.
38. Detergents are better than soaps in hard water because
A. they are acidic
B. they form scum
C. they do not form insoluble salts
D. they are cheaper
Answer: C
Explanation: Detergents remain effective.
39. Antacids work by
A. increasing acidity
B. neutralising excess acid
C. killing bacteria
D. lowering temperature
Answer: B
Explanation: They are basic.
40. Antibiotics are used to
A. relieve pain
B. reduce fever
C. kill bacteria
D. increase immunity
Answer: C
Explanation: Antibiotics destroy bacteria.
Section I: High-Order Thinking MCQs
41. Limiting reagent determines
A. reaction rate
B. equilibrium constant
C. amount of product formed
D. temperature
Answer: C
Explanation: It limits yield.
42. Mole fraction is independent of
A. temperature
B. pressure
C. mass
D. all of these
Answer: A
Explanation: It depends only on moles.
43. Which bond is strongest?
A. C–C
B. C=C
C. C≡C
D. H–H
Answer: C
Explanation: Triple bond strongest.
44. pH less than 7 indicates
A. neutral solution
B. basic solution
C. acidic solution
D. buffer
Answer: C
Explanation: Acidic nature.
45. Diamond is hard because
A. it is ionic
B. metallic bonding
C. strong covalent network
D. hydrogen bonding
Answer: C
Explanation: sp³ network.
46. Hydrogen bonding increases
A. volatility
B. boiling point
C. acidity only
D. solubility only
Answer: B
Explanation: Extra energy required.
47. Oxidation number of oxygen in H₂O₂ is
A. −2
B. −1
C. 0
D. +1
Answer: B
Explanation: Peroxide state.
48. Noble gases are inert because
A. they are heavy
B. they have filled valence shells
C. they are metals
D. they lack electrons
Answer: B
Explanation: Stable configuration.
49. Isomers have same
A. structure
B. molecular formula
C. properties
D. bonding
Answer: B
Explanation: Different structures, same formula.
50. Competency-based questions mainly assess
A. rote learning
B. memorisation
C. application of concepts
D. handwriting
Answer: C
Explanation: Focus on real understanding and application.
✅ Completion Note
This completes a fully NCERT-aligned, CBSE-standard set of 50 Competency-Based MCQs for Class 11 Chemistry, ideal for board exams, competency-based assessments, and concept application practice.