Important Chemistry MCQs for Class 11 Exams
Important Chemistry MCQs for Class 11 Exams
Course: CBSE Class 11 Chemistry – MCQs with Answers and Explanations
Section: Exam-Oriented & Practice-Based Titles
The following 50 Important MCQs are strictly based on the NCERT Class 11 Chemistry syllabus and are curated to cover high-weightage, frequently asked, and conceptually important areas from Physical, Inorganic, and Organic Chemistry. These questions are ideal for CBSE school exams, term exams, and final revision.
Section A: Some Basic Concepts & Mole Concept
1. The SI unit of amount of substance is
A. gram
B. mole
C. kilogram
D. atomic mass unit
Answer: B
Explanation: Mole is the SI unit used to express chemical amount.
2. Number of atoms present in 1 mole of helium is
A. 6.022 × 10²²
B. 3.011 × 10²³
C. 6.022 × 10²³
D. 1.204 × 10²⁴
Answer: C
Explanation: One mole contains Avogadro’s number of particles.
3. Which law states that mass is conserved in a chemical reaction?
A. Law of multiple proportions
B. Law of definite proportions
C. Law of conservation of mass
D. Avogadro’s law
Answer: C
Explanation: Mass of reactants equals mass of products.
4. Which concentration term is temperature dependent?
A. Molality
B. Mole fraction
C. Molarity
D. Mass percent
Answer: C
Explanation: Molarity depends on volume, which changes with temperature.
5. The empirical formula represents
A. actual molecular formula
B. simplest whole-number ratio of atoms
C. number of atoms
D. molecular mass
Answer: B
Explanation: It gives the simplest ratio of atoms in a compound.
Section B: Structure of Atom
6. The maximum number of electrons in an orbital is
A. 1
B. 2
C. 8
D. 18
Answer: B
Explanation: Pauli’s exclusion principle allows only two electrons.
7. Which quantum number determines the shape of an orbital?
A. Principal
B. Azimuthal
C. Magnetic
D. Spin
Answer: B
Explanation: Azimuthal quantum number defines orbital shape.
8. Cathode rays consist of
A. protons
B. neutrons
C. electrons
D. photons
Answer: C
Explanation: Cathode rays are streams of electrons.
9. Bohr’s model is applicable to
A. all atoms
B. multi-electron atoms
C. hydrogen-like atoms
D. molecules
Answer: C
Explanation: It works only for single-electron systems.
10. Aufbau principle explains
A. orbital shape
B. orbital orientation
C. order of filling of orbitals
D. electron spin
Answer: C
Explanation: Orbitals are filled in increasing order of energy.
Section C: Classification of Elements & Periodicity
11. Modern periodic law is based on
A. atomic mass
B. atomic volume
C. atomic number
D. valency
Answer: C
Explanation: Properties are periodic functions of atomic number.
12. Atomic radius decreases across a period due to
A. shielding effect
B. increase in nuclear charge
C. increase in atomic mass
D. decrease in electrons
Answer: B
Explanation: Higher nuclear charge pulls electrons closer.
13. Most electronegative element is
A. Oxygen
B. Nitrogen
C. Chlorine
D. Fluorine
Answer: D
Explanation: Fluorine has highest electronegativity.
14. Ionisation enthalpy generally
A. increases down a group
B. decreases across a period
C. decreases down a group
D. remains constant
Answer: C
Explanation: Increased atomic size lowers ionisation energy.
15. Which element shows maximum metallic character?
A. Lithium
B. Sodium
C. Potassium
D. Cesium
Answer: D
Explanation: Metallic character increases down the group.
Section D: Chemical Bonding
16. VSEPR theory predicts
A. bond energy
B. bond length
C. molecular shape
D. bond polarity
Answer: C
Explanation: Shape is determined by electron pair repulsion.
17. Hybridisation of carbon in methane is
A. sp
B. sp²
C. sp³
D. dsp²
Answer: C
Explanation: Four equivalent sp³ orbitals form.
18. Bond angle in methane is
A. 90°
B. 104.5°
C. 109.5°
D. 120°
Answer: C
Explanation: Tetrahedral bond angle is 109.5°.
19. Strongest repulsion is between
A. bond pair–bond pair
B. bond pair–lone pair
C. lone pair–lone pair
D. all equal
Answer: C
Explanation: Lone pairs occupy more space.
20. Sigma bond is formed by
A. sidewise overlap
B. end-to-end overlap
C. p–p overlap only
D. d–d overlap
Answer: B
Explanation: Head-on overlap forms sigma bonds.
Section E: States of Matter & Thermodynamics
21. Real gases show maximum deviation at
A. high temperature, low pressure
B. low temperature, high pressure
C. normal conditions
D. STP only
Answer: B
Explanation: Intermolecular forces become significant.
22. Ideal gas equation is
A. PV = RT
B. PV = nRT
C. P + V = RT
D. P/T = constant
Answer: B
Explanation: It relates pressure, volume, temperature, and moles.
23. First law of thermodynamics is based on
A. entropy
B. spontaneity
C. conservation of energy
D. equilibrium
Answer: C
Explanation: Energy cannot be created or destroyed.
24. Enthalpy is defined as
A. U − PV
B. U + PV
C. U / V
D. P / V
Answer: B
Explanation: H = U + PV.
25. Endothermic reactions have
A. negative ΔH
B. positive ΔH
C. zero ΔH
D. constant ΔH
Answer: B
Explanation: Heat is absorbed.
Section F: Equilibrium & Redox Reactions
26. Chemical equilibrium is
A. static
B. irreversible
C. dynamic
D. complete
Answer: C
Explanation: Forward and backward reactions occur simultaneously.
27. Equilibrium constant depends on
A. concentration
B. pressure
C. catalyst
D. temperature
Answer: D
Explanation: K changes only with temperature.
28. Oxidation involves
A. gain of electrons
B. loss of electrons
C. gain of neutrons
D. loss of protons
Answer: B
Explanation: Oxidation is loss of electrons.
29. An oxidising agent
A. gets oxidised
B. loses electrons
C. gains electrons
D. remains unchanged
Answer: C
Explanation: It accepts electrons and gets reduced.
30. pH of neutral solution at 25°C is
A. 0
B. 7
C. 14
D. 1
Answer: B
Explanation: Neutral solutions have pH 7.
Section G: s-Block and p-Block Elements
31. Alkali metals have general configuration
A. ns²
B. ns¹
C. ns²np¹
D. ns²np⁶
Answer: B
Explanation: One valence electron makes them highly reactive.
32. Lithium shows anomalous behaviour due to
A. large size
B. diagonal relationship
C. inert pair effect
D. metallic bonding
Answer: B
Explanation: Lithium resembles magnesium diagonally.
33. Boron compounds are mainly
A. ionic
B. covalent
C. metallic
D. amphoteric
Answer: B
Explanation: High ionisation energy prevents ionic bonding.
34. Carbon shows maximum catenation because
A. it is metallic
B. C–C bond is strong
C. it has large size
D. it forms ionic bonds
Answer: B
Explanation: Strong C–C bonds allow long chains.
35. 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 forms acid in water.
Section H: Organic Chemistry & Environmental Chemistry
36. Organic chemistry mainly deals with
A. metals
B. carbon compounds
C. salts
D. acids only
Answer: B
Explanation: Carbon forms vast number of compounds.
37. Members of homologous series differ by
A. functional group
B. –CH₂– group
C. molecular mass only
D. name
Answer: B
Explanation: Successive members differ by –CH₂– unit.
38. Alkenes undergo addition reactions due to
A. sigma bond
B. pi bond
C. hydrogen bond
D. ionic bond
Answer: B
Explanation: Pi bond is weaker and reactive.
39. Ozone depletion is mainly caused by
A. CO₂
B. SO₂
C. CFCs
D. NO₂
Answer: C
Explanation: Chlorine radicals destroy ozone.
40. Detergents are better than soaps in hard water because they
A. are acidic
B. do not form scum
C. are cheaper
D. are natural
Answer: B
Explanation: Detergents do not form insoluble salts.
Section I: High-Scoring Revision MCQs
41. Limiting reagent determines
A. reaction rate
B. amount of product formed
C. equilibrium constant
D. temperature
Answer: B
Explanation: It limits the maximum yield.
42. Mole fraction is
A. temperature dependent
B. pressure dependent
C. dimensionless
D. mass dependent
Answer: C
Explanation: It is a ratio of moles.
43. Strongest bond among C–C, C=C and C≡C is
A. C–C
B. C=C
C. C≡C
D. H–H
Answer: C
Explanation: Triple bond has highest bond energy.
44. Hydrogen bonding increases
A. volatility
B. boiling point
C. acidity only
D. density only
Answer: B
Explanation: Extra energy required to break H-bonds.
45. Diamond is hard because
A. it is ionic
B. metallic bonding
C. strong covalent network
D. hydrogen bonding
Answer: C
Explanation: Rigid sp³ covalent structure.
46. Oxidation number of oxygen in H₂O₂ is
A. −2
B. −1
C. 0
D. +1
Answer: B
Explanation: Peroxides have −1 oxidation state.
47. Isomers have same
A. structure
B. molecular formula
C. properties
D. bonding
Answer: B
Explanation: Different structures but same formula.
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 electronic configuration.
49. pH less than 7 indicates
A. neutral solution
B. basic solution
C. acidic solution
D. buffer
Answer: C
Explanation: Acidic solutions have pH < 7.
50. Best strategy for scoring high in Chemistry exams is
A. rote learning
B. memorising formulas
C. regular MCQ practice
D. reading notes once
Answer: C
Explanation: MCQs improve speed, accuracy, and concept clarity.
✅ Completion Note
This completes a highly exam-focused, NCERT-aligned set of 50 Important MCQs for CBSE Class 11 Chemistry, ideal for revision, unit tests, and final exam preparation.