NCERT Solutions Class 11 Chemistry - All 14 Chapters

All 14 Chapters

Some Basic Concepts of Chemistry

Mole concept, Stoichiometry

› 2

Structure of Atom

Bohr model, Quantum numbers

› 3

Classification of Elements

Periodic table, Periodicity

› 4

Chemical Bonding

Ionic, Covalent, VSEPR, VBT

› 5

States of Matter

Gases, Liquids, Intermolecular forces

› 6

Thermodynamics

Enthalpy, Entropy, Gibbs energy

› 7

Equilibrium

Kc, Kp, pH, Buffer solutions

› 8

Redox Reactions

Oxidation number, Balancing

› 9

Hydrogen

Isotopes, Water, Heavy water

› 10

s-Block Elements

Alkali metals, Alkaline earth metals

› 11

p-Block Elements

Group 13 and 14

› 12

Organic Chemistry - Basic Principles

IUPAC naming, Isomerism, Reaction intermediates

› 13

Hydrocarbons

Alkanes, Alkenes, Alkynes, Aromatic

› 14

Environmental Chemistry

Air pollution, Water pollution, Ozone depletion

›

Chapter 1: Some Basic Concepts of Chemistry

Q1. Calculate the number of moles in 54 g of water.

Solution

Molar mass of H₂O = 18 g/mol
Moles = 54/18 = 3 mol

Q2. What is the empirical formula of a compound with 40% C, 6.7% H and 53.3% O?

Solution

C: 40/12 = 3.33, H: 6.7/1 = 6.7, O: 53.3/16 = 3.33
Ratio = 1:2:1
Empirical formula = CH₂O

Q3. Find the mass of 0.5 mol of NaCl.

Solution

Molar mass = 58.5 g/mol
Mass = 0.5 × 58.5 = 29.25 g

Chapter 2: Structure of Atom

• n = 1, 2, 3, ... (principal quantum number)
• l = 0 to n-1 (azimuthal)
• m_l = -l to +l (magnetic)
• m_s = ±⅔ (spin)

Q1. How many orbitals are possible for n = 3?

Solution

l = 0, 1, 2
Number of orbitals = 1 + 3 + 5 = 9

Q2. Write the electronic configuration of Fe (Z = 26).

Solution

[Ar] 3d² 4s² or 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s²

Q3. Calculate the de Broglie wavelength of an electron moving at 2 × 10⁴ m/s.

Solution

λ = h/mv = 6.63 × 10⁻⁴⁹ / (9.1 × 10⁻⁳⁷ × 2 × 10⁴)
= 3.64 × 10⁻⁺ m

Chapter 3: Classification of Elements and Periodicity

Q1. Arrange Na, Mg, Al in increasing order of atomic radius.

Solution

Atomic radius decreases across a period due to increased nuclear charge.

Al < Mg < Na

Q2. Which has higher ionization energy: N or O? Why?

Solution

N has higher ionization energy than O because N has a half-filled 2p subshell which is extra stable.

Chapter 4: Chemical Bonding and Molecular Structure

Q1. Draw the Lewis structure of CO₂.

Solution

O=C=O with two double bonds
Linear shape, sp hybridization

Q2. What is the shape of NH₃ according to VSEPR?

Solution

3 bonding pairs + 1 lone pair = trigonal pyramidal

Q3. Distinguish between sigma and pi bonds.

Solution

Sigma (σ) bond: Formed by head-on overlap, stronger
Pi (π) bond: Formed by sideways overlap, weaker

Chapter 5: States of Matter

• PV = nRT (ideal gas law)
• P_total = P₁ + P₂ (Dalton's law)
• PVγ = constant (adiabatic)

Q1. Find the pressure of 2 mol of gas at 300K occupying 5 L. (R = 0.0821 L atm/mol K)

Solution

P = nRT/V = (2 × 0.0821 × 300)/5 = 9.852 atm

Q2. At what temperature will 1 mol of gas occupy 22.4 L at 1 atm?

Solution

T = PV/nR = (1 × 22.4)/(1 × 0.0821) = 273 K (0°C)

Chapter 6: Thermodynamics

• ∆H = ∆U + P∆V
• ∆G = ∆H - T∆S
• q = mc∆T

Q1. Calculate ∆G if ∆H = 100 kJ and ∆S = 200 J/K at 300K.

Solution

∆G = ∆H - T∆S
= 100000 - 300 × 200 = 100000 - 60000 = 40 kJ

Chapter 7: Equilibrium

• K_c = [Products]/[Reactants]
• K_p = K_c(RT)^∆n
• pH = -log[H₁]
• K_w = 10⁻²²

Q1. Find the pH of 0.01 M HCl solution.

Solution

pH = -log(0.01) = -log(10⁻²) = 2

Q2. What is the [H₁] of a solution with pH = 5?

Solution

[H₁] = 10⁻^pH = 10⁻⁵ M = 1 × 10⁻⁵ M

Chapter 8: Redox Reactions

Q1. Balance: Fe + O₂ → Fe₂O₃

Solution

4Fe + 3O₂ → 2Fe₂O₃

Q2. Find the oxidation number of Cr in K₂Cr₂O₇.

Solution

2(+1) + 2(x) + 7(-2) = 0
2 + 2x - 14 = 0
2x = 12, x = +6

Chapter 9: Hydrogen

Q1. What is the difference between heavy water and ordinary water?

Solution

Ordinary water: H₂O
Heavy water: D₂O (Deuterium oxide)
Heavy water is used as moderator in nuclear reactors.

Q2. Name the three isotopes of hydrogen.

Solution

1. Protium (₁⁶H)
2. Deuterium (₂⁶H or D)
3. Tritium (₃⁶H or T)

Chapter 10: s-Block Elements

Q1. Why are alkali metals stored in kerosene?

Solution

Alkali metals are highly reactive and react with moisture and air. They are stored in kerosene to prevent contact with air and moisture.

Q2. What happens when Na is heated in excess air?

Solution

2Na + O₂ → Na₂O₂ (sodium peroxide)

Chapter 11: p-Block Elements (Group 13 & 14)

Q1. Why does aluminium form Al₂Cl₆ instead of AlCl₃?

Solution

Aluminium has vacant d-orbitals and can expand its coordination number to 6 by forming Al₂Cl₆ (dimer) to complete its octet.

Q2. What is the inert pair effect?

Solution

The tendency of the two electrons in the outermost s-orbital to remain unshared in post-transition metals. It causes elements to show oxidation states 2 less than their group valency.

Chapter 12: Organic Chemistry - Basic Principles

Q1. Give the IUPAC name of CH₃CH₂CH₂OH.

Solution

Propan-1-ol

Q2. What are the differences between SN1 and SN2 reactions?

Solution

SN1: Two steps, racemization, 3° substrate preferred
SN2: One step, inversion, 1° substrate preferred

Chapter 13: Hydrocarbons

Q1. Write the reactions for the combustion of methane.

Solution

CH₄ + 2O₂ → CO₂ + 2H₂O

Q2. What is Markovnikov's rule?

Solution

When HX adds to an unsymmetrical alkene, the hydrogen adds to the carbon with more hydrogen atoms, and X adds to the carbon with fewer hydrogen atoms.

Chapter 14: Environmental Chemistry

Q1. What causes acid rain?

Solution

SO₂ and NO₂ released from vehicles and industries combine with water vapor to form H₂SO₄ and HNO₃.

Q2. What is the role of CFCs in ozone depletion?

Solution

CFCs release chlorine radicals in the stratosphere which catalytically destroy ozone: Cl + O₃ → ClO + O₂