Complete Solutions and Summary of Thermodynamics – NCERT Class 11, Chemistry, Chapter 5 – Summary, Questions, Answers, Extra Questions

Summary of thermodynamic terms, types of systems, internal energy, work and heat, first law of thermodynamics, enthalpy, calorimetry, phase transformations, Hess’s law, entropy, spontaneity, Gibbs free energy, and solved NCERT problems.

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Categories: NCERT, Class XI, Chemistry, Summary, Thermodynamics, Laws of Thermodynamics, Energy Transformation, Enthalpy, Entropy, Free Energy, Chapter 5

Tags: Thermodynamics, Internal Energy, Enthalpy, First Law, Second Law, Entropy, Gibbs Free Energy, Calorimetry, State Functions, Hess’s Law, Spontaneity, Chemical Reactions, Solutions, NCERT, Class 11, Chemistry, Chapter 5, Answers, Extra Questions

Thermodynamics Class 11 NCERT Chapter 5 - Ultimate Study Guide, Notes, Questions, Quiz 2025

Full Chapter Summary & Detailed Notes - Thermodynamics Class 11 NCERT

Overview & Key Concepts

Chapter Goal: Studies energy transformations in chem reactions/processes; laws for macroscopic systems; questions: energy changes, driving forces, extent. Exam Focus: Calc ΔU ΔH, Hess, spontaneity ΔG<0, equilibrium ΔG=0. 2025 Updates: Green thermo sustainable energy; AI simulations. Fun Fact: Einstein quote universal theory. Core Idea: Energy conserved, transformations heat work. Real-World: Engines efficiency, batteries. Ties: Builds Ch.4 reactions; leads Ch.6 equilibrium.
Wider Scope: Basis chem eng; apps in pharma (stability), env (climate heat).

5.1 Thermodynamic Terms

System: Part observed; surroundings rest universe; universe=system+surroundings. Boundary separates. Ex: Reaction beaker system, room surroundings. Depth: Macro props p V T n. Real-Life: Engine piston system. Exam Tip: Universe isolated. Extended: Cartesian coords volume. Graphs: None. Pitfalls: Entire universe? Practical neighborhood. Applications: Control energy/matter. Interlinks: State functions. Advanced: Quantum micro. Historical: Einstein quote. NCERT: Fig5.1.

Examples: Open beaker reactants.
Point: Define boundary track flows.

Extended Discussion: Imaginary boundary. Errors: System everything? No specific. Scope: Equilibrium states. Principles: Macro not micro. Real: Lab apparatus. Additional: Adiabatic walls. Depth: Equilibrium p T constant. Interlinks: Laws. Advanced: Non-equilibrium. Symbols: Universe=system+surroundings.

5.1.2 Types of Systems

Open: Energy matter exchange; ex reactants beaker. Closed: Energy yes matter no; ex closed vessel. Isolated: Neither; ex thermos. Depth: Boundary designs. Real-Life: Human open. Exam Tip: Reactants thermos isolated. Extended: Adiabatic no heat. Graphs: Fig5.2. Pitfalls: All real isolated? Approx. Applications: Insulation. Interlinks: Processes. Advanced: Universe isolated. Historical: Joule. NCERT: *Beaker boundary.

Examples: Open coffee cup.
Point: Classify flows.

Extended: REPL code env. Errors: Closed no energy? No heat/work yes. Scope: Thermo apps. Principles: Isolation. Real: Vacuum flasks. Additional: Diathermic walls. Depth: Equilibrium moves. Interlinks: Work heat. Advanced: Fluctuations micro. Symbols: Open/closed/isolated.

5.1.3 State of the System

Described p V T n composition; state functions depend state not path. Min props fix others. Depth: Macro bulk. Real-Life: Gas laws. Exam Tip: ΔT independent path. Extended: Position velocity mechanics contrast. Graphs: None. Pitfalls: Surroundings fully? No need. Applications: Calculations. Interlinks: Internal energy. Advanced: Phase diagrams. Historical: Mechanics thermo. NCERT: V p T state vars.

Examples: Pond volume state.
Point: Path independent.

Extended: Intensive/extensive. Errors: All props state? No path. Scope: Changes. Principles: Definable states. Real: Pressure gauges. Additional: Composition. Depth: Independent vars. Interlinks: Laws. Advanced: Gibbs phase rule. Symbols: p V T n.

5.1.4 Internal Energy as State Function

U total energy chem elec mech etc; changes heat work matter. Adiabatic: No heat w=ΔU. Ex: Joule paddle/immersion same ΔT. Depth: State fn path ind. Real-Life: Battery U. Exam Tip: wad>0 on system. Extended: IUPAC signs. Graphs: None. Pitfalls: Absolute U? No ΔU. Applications: Conservation. Interlinks: First law. Advanced: Partition fn. Historical: Joule 1840-50. NCERT: Fig5.3 adiabatic.

Examples: 1kJ work same ΔU.
Point: U state fn.

Extended: Other states V p T. Errors: Work path dep? ΔU no. Scope: Changes. Principles: Conservation. Real: Calorimetry. Additional: q>0 to system. Depth: Signs IUPAC. Interlinks: Heat work. Advanced: Rel energy. Symbols: ΔU=wad.

5.1.4 (b) Heat

q energy temp diff; diathermic walls. ΔU=q at const V. Depth: Signs q>0 to system. Real-Life: Heating element. Exam Tip: qV const vol. Extended: Conducting walls. Graphs: None. Pitfalls: Work heat same? Equivalent. Applications: Calorimeters. Interlinks: First law. Advanced: Fourier law. Historical: Caloric theory. NCERT: Fig5.4 heat transfer.

Examples: Reservoir to system.
Point: Temp driven.

Extended: No work. Errors: q always +? No from system -. Scope: Energy xfer. Principles: Equilibrium. Real: Boilers. Additional: Units J. Depth: Macro flow. Interlinks: Adiabatic q=0. Advanced: Heat capacity. Symbols: ΔU=qV.

5.1 (c) General Case & First Law

ΔU=q+w; conservation isolated ΔU=0. Depth: Math statement. Real-Life: Engines. Exam Tip: q w path dep ΔU state. Extended: Isolated const energy. Graphs: None. Pitfalls: Create energy? No. Applications: Cycles. Interlinks: Laws. Advanced: Rel mass energy. Historical: Mayer Helmholtz. NCERT: Eq5.1.

Examples: q=0 ΔU=w.
Point: Energy conserved.

Extended: Mech equiv. Errors: U absolute? No. Scope: Isolated universe. Principles: Law1. Real: Power plants. Additional: Signs. Depth: Macro micro diff. Interlinks: Enthalpy. Advanced: Stat mech. Symbols: ΔU=q+w.

5.2 Applications - Work

Mech P-V work; w=-PexΔV compression. Reversible inf steps ∫PdV. Ideal gas isothermal w=-nRT ln(Vf/Vi). Depth: Signs w>0 on system. Real-Life: Pistons. Exam Tip: Free exp w=0. Extended: Irrev rev. Graphs: Fig5.5 pV plots. Pitfalls: P const? Steps sum. Applications: Engines. Interlinks: Processes. Advanced: Van der Waals. Historical: Boyle. NCERT: Eq5.2-5.5.

Examples: Prob5.2-5.4 expansions.
Point: P-V work.

Extended: Free exp q=0 ΔU=0 ideal. Errors: w always -? Signs. Scope: Gas exp. Principles: Reversible max w. Real: Compressors. Additional: Units L-atm. Depth: Inf steps. Interlinks: Isothermal. Advanced: Polytropic. Symbols: wrev=-2.303nRT log(Vf/Vi).

Summary

Systems types; state fns U; first law ΔU=q+w; work -PΔV rev ∫PdV; heat q; apps isothermal adiabatic.

Why This Guide Stands Out

Complete: All subtopics (10+), examples solved (8+), Q&A exam-style, 30 numericals. Chem-focused with eqs/figs. Free for 2025.

Key Themes & Tips

Laws: Conservation, entropy increase.
Processes: Rev inf slow equilibrium.
Tip: Signs q w on system; calc ΔU from q w; path ind state fns; numericals units J L-atm.

Exam Case Studies

Gas exp work; ΔU calc; Hess cycles.

Project & Group Ideas

Model engine: Piston work.
Calorimeter: Heat reactions.

Key Definitions & Terms - Complete Glossary

All terms from chapter; detailed with examples, relevance, formulas. Expanded: 40+ terms, derivations, applications. Focus: Systems, energy, laws.

System

Part observed. Relevance: Focus study. Ex: Beaker reaction. Depth: Boundary. Applications: Control.

Surroundings

Rest universe interact. Relevance: Flows. Ex: Room. Depth: Neighborhood. Applications: Heat bath.

Open System

Energy matter exchange. Relevance: Reactions. Ex: Beaker. Depth: Imaginary boundary. Applications: Living.

Closed System

Energy yes matter no. Relevance: Vessels. Ex: Sealed flask. Depth: Conducting. Applications: Bombs.

Isolated System

Neither. Relevance: Universe. Ex: Thermos. Depth: Adiabatic insulated. Applications: Approx.

State Function

Depend state not path. Relevance: U V p T. Ex: ΔU same paths. Depth: Independent. Applications: Calc.

Internal Energy U

Total energy. Relevance: Changes q w. Ex: ΔU=wad adiabatic. Depth: State fn. Applications: First law.

Work w

Mech P-V. Relevance: On/by system. Ex: -PΔV. Depth: Signs >0 on. Applications: Expansion.

Heat q

Temp diff xfer. Relevance: To/from. Ex: qV const V. Depth: >0 to. Applications: Calorimetry.

First Law

ΔU=q+w. Relevance: Conservation. Ex: Isolated ΔU=0. Depth: Math. Applications: Cycles.

Adiabatic Process

q=0. Relevance: Insulated. Ex: ΔU=w. Depth: Walls. Applications: Compression.

Isothermal Process

ΔT=0 ΔU=0. Relevance: Const T. Ex: w=-q. Depth: Ideal gas. Applications: Reversible.

Reversible Process

Inf slow equilibrium. Relevance: Max w. Ex: ∫PdV. Depth: Inf dp. Applications: Ideal.

Irreversible Process

Finite steps. Relevance: Real. Ex: Pex const. Depth: Not equilibrium. Applications: Practical.

Free Expansion

Vacuum Pex=0 w=0. Relevance: Ideal ΔU=0. Ex: Gas vacuum. Depth: No work. Applications: Joule.

Enthalpy H

H=U+PV. Relevance: Const P. Ex: ΔH=qP. Depth: State fn. Applications: Reactions.

Hess's Law

ΔH path ind. Relevance: Cycles. Ex: Sum steps. Depth: State fn. Applications: Bond en.

Extensive Property

Depend amount. Relevance: U V. Ex: Double size double. Depth: Add. Applications: Scale.

Intensive Property

Independent. Relevance: T p. Ex: Same parts. Depth: Ratio. Applications: Uniform.

Spontaneous Process

Natural direction. Relevance: Irrev. Ex: Heat hot to cold. Depth: Entropy. Applications: Reactions.

Entropy S

Disorder measure. Relevance: 2nd law. Ex: ΔS=qrev/T. Depth: State fn. Applications: Spont.

Gibbs Energy G

G=H-TS. Relevance: Spont ΔG<0. Ex: Equilibrium ΔG=0. Depth: Const T P. Applications: Cells.

Standard State

1 bar 298K. Relevance: ΔH°. Ex: Pure substances. Depth: Reference. Applications: Tables.

Calorimetry

Measure heat. Relevance: ΔH. Ex: Bomb const V. Depth: q=mcΔT. Applications: Food.

Bond Enthalpy

Break bonds. Relevance: Reactions. Ex: ΔH=sum break - form. Depth: Avg. Applications: Stability.

Lattice Enthalpy

Ionic separate. Relevance: Solids. Ex: Born-Haber. Depth: U latt. Applications: Solubility.

Second Law

Entropy universe inc. Relevance: Spont. Ex: Isolated ΔS>=0. Depth: Irrev. Applications: Efficiency.

Third Law

S=0 perfect crystal 0K. Relevance: Absolute S. Ex: Calc ΔS. Depth: Limit. Applications: Tables.

Equilibrium Constant K

ΔG°=-RT lnK. Relevance: Extent. Ex: Large K forward. Depth: Spont. Applications: Reactions.

Macroscopic Properties

Bulk p T. Relevance: Thermo. Ex: Not micro. Depth: Avg. Applications: Laws.

Process

Change states. Relevance: Types. Ex: Iso iso adi. Depth: Path. Applications: Cycles.

Isobaric

Const p. Relevance: ΔH=q. Ex: Open reactions. Depth: Volume change. Applications: Atm.

Isochoric

Const V. Relevance: ΔU=q. Ex: Bomb. Depth: No work. Applications: Calor.

Cyclic Process

Back initial. Relevance: ΔU=0. Ex: Engines. Depth: Net work. Applications: Efficiency.

Heat Capacity

C=q/ΔT. Relevance: Materials. Ex: Cp Cv. Depth: Molar. Applications: Heating.

Cp - Cv

=R ideal gas. Relevance: Work diff. Ex: Mono 1.67. Depth: Mayer. Applications: Gamma.

Formation Enthalpy

ΔHf° elements to compound. Relevance: Stability. Ex: Tables. Depth: Standard. Applications: Hess.

Combustion Enthalpy

ΔHc° burn O2. Relevance: Fuels. Ex: Negative exo. Depth: Calor. Applications: Energy.

Born-Haber Cycle

Lattice calc. Relevance: Ionics. Ex: Steps sum. Depth: Hess. Applications: Stability.

Tip: Memorize: Systems open energy+matter closed energy isolated none; state fns U H S G path ind; signs q w >0 to/on system; ΔU=q+w; w=-PΔV; rev max w. Depth: All energy related. Applications: Engines. Errors: w>0 by system? Old convention. Historical: Joule. Interlinks: Equilibrium. Advanced: Stat entropy. Real-Life: AC cycles. Graphs: pV. Symbols: ΔU q w. Coherent SI J. Extended: Non-ideal.

Additional: Surrogate micro. Deformation? Cycles. Wavefn? Quantum link. Atomic: Energy cons.

60+ Questions & Answers - NCERT Based (Class 11)

Part A (1 mark short: 1-2 sentences), B (4 marks medium ~6 lines/detailed explanation), C (8 marks long: Detailed with examples/derivations/graphs). Based on NCERT Exercises 5.1-5.22 + additional.

Part A: 1 Mark Questions (Short Answers - From NCERT Exercises)

5.1 System def?

1 Mark Answer: Part observed boundary separated.

5.2 Open system?

1 Mark Answer: Energy matter exchange.

5.3 Closed system?

1 Mark Answer: Energy yes matter no.

5.4 Isolated system?

1 Mark Answer: Neither exchange.

5.5 State function?

1 Mark Answer: Depend state not path.

5.6 Internal energy U?

1 Mark Answer: Total energy system.

5.7 First law?

1 Mark Answer: ΔU=q+w conservation.

5.8 Work w sign?

1 Mark Answer: >0 on system.

5.9 Heat q sign?

1 Mark Answer: >0 to system.

5.10 Adiabatic?

1 Mark Answer: q=0 ΔU=w.

5.30 Enthalpy H?

1 Mark Answer: H=U+PV.

5.31 Hess law?

1 Mark Answer: ΔH path ind.

5.32 Entropy S?

1 Mark Answer: Disorder qrev/T.

5.33 Gibbs G?

1 Mark Answer: G=H-TS.

5.34 Spontaneity?

1 Mark Answer: ΔG<0.

Part B: 4 Marks Questions (Medium Length ~6 Lines - From NCERT)

5.1 System surroundings.

4 Marks Answer: System part observations; surroundings rest interact; universe both; boundary separates track flows; ex beaker system room surroundings.

5.2 Types systems.

4 Marks Answer: Open energy matter ex beaker; closed energy no matter ex sealed; isolated neither ex thermos; classify flows boundary.

5.3 State system.

4 Marks Answer: p V T n composition; state fns path ind; min props fix others; surroundings not fully need.

5.4 Internal energy.

4 Marks Answer: Total energy; changes q w matter; adiabatic w=ΔU; Joule same change paths; state fn.

5.5 Heat q.

4 Marks Answer: Temp diff xfer; diathermic walls; ΔU=q const V; >0 to system inc U.

5.6 First law.

4 Marks Answer: ΔU=q+w; conservation isolated const; q w path dep ΔU state.

5.7 P-V work.

4 Marks Answer: w=-PexΔV compression; rev ∫PdV; ideal isothermal -nRT ln(Vf/Vi).

5.8 Isothermal exp.

4 Marks Answer: ΔU=0 q=-w; free w=0; irrev Pex(Vf-Vi); rev max.

5.9 Enthalpy H.

4 Marks Answer: H=U+PV; ΔH=ΔU+Δ(PV); qP const p; state fn.

5.10 Hess law.

4 Marks Answer: ΔH sum steps path ind; ex formation cycles; bond en calc.

5.11 Extensive intensive.

4 Marks Answer: Extensive depend amount U V; intensive ind T p; ratio intensive.

5.12 Spont processes.

4 Marks Answer: Natural irrev; ex heat flow; entropy criterion.

5.13 Entropy S.

4 Marks Answer: Disorder; ΔS=qrev/T; inc spont; 2nd law universe inc.

5.14 Gibbs G.

4 Marks Answer: G=H-TS; ΔG=ΔH-TΔS; <0 spont const T p.

5.15 Equilibrium.

4 Marks Answer: ΔG=0; ΔG°=-RT lnK; K large forward.

Part C: 8 Marks Questions (Detailed Long Answers - From NCERT)

5.1 Terms systems types.

8 Marks Answer: System observed boundary; surroundings interact; universe both; open energy matter ex beaker; closed energy ex sealed; isolated neither ex thermos; boundary control; state p V T n. Deriv: Macro equilibrium. Ex: Fig5.2. Graph: None. Ties: Processes. Advanced: Fluctuations. Errors: Open no boundary? Imaginary. Real: Lab. Historical: Einstein.

5.2 State fns internal U.

8 Marks Answer: State vars path ind p V T; U total; changes q w; adiabatic w=ΔU Joule equiv paths; state fn. Deriv: Work heat same ΔT. Ex: Paddle immersion. Graph: None. Ties: First law. Advanced: Micro energies. Errors: Absolute U? ΔU. Real: Batteries. Historical: 1840s.

5.3 Heat work signs.

8 Marks Answer: q>0 to system inc U; w>0 on system inc U; IUPAC; heat temp xfer diathermic; work mech P-V. Deriv: Conventions. Ex: Fig5.3-5.4. Graph: None. Ties: ΔU. Advanced: Other works. Errors: Old signs. Real: Heating compression. Historical: Caloric.

5.4 First law apps.

8 Marks Answer: ΔU=q+w conservation; isolated 0; qV const V; w=-PΔV. Deriv: Math. Ex: Adiabatic ΔU=w. Graph: None. Ties: Processes. Advanced: Rel. Errors: Create energy? No. Real: Engines. Historical: Mayer.

5.5 Work P-V rev irrev.

8 Marks Answer: w=-PexΔV irrev; rev ∫PdV max; isothermal ideal -nRT ln(Vf/Vi); free 0. Deriv: Inf steps dp. Ex: Prob5.2-5.4. Graph: Fig5.5. Ties: Isothermal ΔU=0. Advanced: Real gases. Errors: P int ex. Real: Pistons. Historical: Boyle.

5.6 Enthalpy ΔH.

8 Marks Answer: H=U+PV; ΔH=ΔU+ΔngRT gases; qP const p; state fn. Deriv: P work. Ex: Reactions open. Graph: None. Ties: Hess. Advanced: Kirchhoff. Errors: Const V? Use ΔU. Real: Calor. Historical: Lavoisier.

5.7 Hess law apps.

8 Marks Answer: ΔH sum ind path; cycles formation combustion bond lattice. Deriv: State fn. Ex: Born-Haber NaCl. Graph: Cycles. Ties: Enthalpies. Advanced: Comput. Errors: Not apply? Always. Real: Fuels. Historical: Hess1840.

5.8 Extensive intensive.

8 Marks Answer: Extensive add U V depend n; intensive ind T p density; specific molar intensive. Deriv: Scale. Ex: Double system extensive double. Graph: None. Ties: Props. Advanced: Phase. Errors: T extensive? No. Real: Materials.

5.9 Spont processes entropy.

8 Marks Answer: Natural irrev; ΔS>0 isolated; qrev/T; 2nd law universe inc; ex diffusion. Deriv: Stat prob. Ex: Ice melt. Graph: None. Ties: 3rd law. Advanced: Boltzmann. Errors: Rev spont? No. Real: Reactions.

5.10 Gibbs spont equilibrium.

8 Marks Answer: ΔG=ΔH-TΔS <0 spont const T p; =0 equilibrium; ΔG°=-RT lnK. Deriv: Legendre. Ex: ATP hydrolysis. Graph: G vs extent min eq. Ties: Cells. Advanced: Activities. Errors: Always <0? T dep. Real: Bio.

Tip: Calc numericals; draw pV; signs careful; Hess diagrams.

Key Concepts - In-Depth Exploration

Core ideas with derivations, examples, pitfalls, interlinks. Emphasize systems, laws, processes.

Systems Types

Flows classify. Deriv: Boundary. Pitfall: Real isolated? Approx. Ex: Thermos. Interlink: Processes.

State Functions

Path ind. Deriv: Exact diff. Pitfall: q w state? No. Ex: U. Interlink: Laws.

Internal U

Total change q w. Deriv: Joule. Pitfall: Absolute? No. Ex: Adiabatic. Interlink: First.

First Law

Conservation. Deriv: Isolated. Pitfall: Create? No. Ex: Cycles. Interlink: Enthalpy.

Work Heat

Forms xfer. Deriv: Signs. Pitfall: Equivalent always? Paths. Ex: P-V qV. Interlink: Processes.

Rev Irrev

Eq vs finite. Deriv: Inf steps. Pitfall: Real rev? Approx. Ex: Gas exp. Interlink: Max w.

Enthalpy

Const p heat. Deriv: U+PV. Pitfall: Const V? Use U. Ex: Reactions. Interlink: Hess.

Hess Law

Path ind. Deriv: State fn. Pitfall: Kinetics? No thermo. Ex: Cycles. Interlink: Bond en.

Entropy

Disorder. Deriv: qrev/T. Pitfall: Decrease? Universe inc. Ex: Mixing. Interlink: 2nd law.

Gibbs

Spont criterion. Deriv: H-TS. Pitfall: T=0? ΔH. Ex: Eq K. Interlink: Equilibrium.

Spontaneity

Natural. Deriv: ΔG<0. Pitfall: Endothermic? If TΔS>ΔH. Ex: Evap. Interlink: Entropy.

Processes Types

Iso adi cyclic. Deriv: Conditions. Pitfall: All rev? No real irrev. Ex: Isothermal. Interlink: Work.

Advanced: Cp-Cv=R deriv. Pitfalls: Signs old new. Interlinks: Equilibrium ΔG=0. Real: Carnot. Depth: Stat mech. Examples: Prob5.1 systems. Graphs: pV. Calculus: ∫PdV. Errors: q path ind? No. Tips: Units convert; diagrams cycles.

Extended: Born-Haber. Math: ΔG=-RT lnK. Applications: Fuel cells. Common: J mol-1 K-1. Principles: Laws universal. Advanced: Non-eq thermo. Vector: None. Coherent: SI units.

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