Thermodynamics & Thermochemistry Class 11 Chemistry: All Formulas & Formula Sheet with Free PDF Download (JEE & NEET)
Thermodynamics & Thermochemistry Class 11 Chemistry — Competishun
Thermodynamics & Thermochemistry Class 11 Chemistry: All Formulas & Formula Sheet with Free PDF Download (JEE & NEET)
Thermodynamics and Thermochemistry is one of the most important and formula-rich chapters in Class 11 chemistry, and it carries strong weightage in JEE and NEET. It studies energy changes in chemical reactions, using ideas like internal energy, enthalpy, entropy and Gibbs free energy to predict whether a reaction will happen at all.
This page gives you the complete Thermodynamics and Thermochemistry formula sheet for Class 11 in one place: the first law, enthalpy, heat capacity, processes, Hess's law, bond enthalpy, entropy and Gibbs free energy, with worked examples. Download the free PDF below and keep it handy for revision.
Download the Thermodynamics & Thermochemistry Formula Sheet PDF
Get all Thermodynamics and Thermochemistry formulas, the laws, enthalpy, entropy and Gibbs free energy in one clean PDF, free. Perfect for Class 11, JEE and NEET revision.
Download Free PDFKey Terms You Must Know
| Term | Meaning |
|---|---|
| System | The part of the universe under study |
| Surroundings | Everything outside the system |
| Open system | Exchanges both matter and energy |
| Closed system | Exchanges energy but not matter |
| Isolated system | Exchanges neither matter nor energy |
| State function | Depends only on state (U, H, S, G, P, V, T) |
| Path function | Depends on the path (q, W) |
| Extensive / Intensive | Depends on amount (U, V) / independent of amount (T, P, density) |
| State functions depend only on initial and final states, path functions depend on how you get there. | |
1. First Law of Thermodynamics
| Concept | Formula |
|---|---|
| First law | ΔU = q + W |
| Work of expansion | W = −P_ext ΔV |
| Enthalpy definition | H = U + PV |
| Enthalpy-internal energy | ΔH = ΔU + Δn_g RT |
| Heat at constant V | q_v = ΔU |
| Heat at constant P | q_p = ΔH |
| Sign convention: heat added to system is +q, work done on system is +W. Δn_g = moles of gaseous products − reactants. | |
2. Heat Capacity
| Concept | Formula |
|---|---|
| Heat absorbed | q = m c ΔT = n C ΔT |
| Molar heat capacities (ideal gas) | C_p − C_v = R |
| Ratio of heat capacities | γ = C_p / C_v |
| Monatomic gas | C_v = (3/2)R, C_p = (5/2)R |
| C_p is always greater than C_v because at constant pressure some heat also does expansion work. | |
3. Thermodynamic Processes
| Process | Condition | Key Result |
|---|---|---|
| Isothermal | T constant, ΔU = 0 | q = −W = 2.303 nRT log(V₂/V₁) |
| Adiabatic | q = 0 | ΔU = W, PVγ = constant |
| Isobaric | P constant | q = ΔH, W = −PΔV |
| Isochoric | V constant | W = 0, q = ΔU |
| Cyclic | returns to start | ΔU = 0, ΔH = 0 |
| Isothermal reversible work: W = −2.303 nRT log(V₂/V₁). | ||
4. Thermochemistry: Enthalpy of Reactions
| Concept | Formula / Rule |
|---|---|
| Enthalpy of reaction | ΔH = ΣH(products) − ΣH(reactants) |
| From enthalpies of formation | ΔH°_rxn = ΣΔH°_f(products) − ΣΔH°_f(reactants) |
| Exothermic / Endothermic | ΔH < 0 (releases heat) / ΔH > 0 (absorbs heat) |
| Hess's law | ΔH is same in one step or many steps |
| Bond enthalpy method | ΔH = Σ BE(reactants) − Σ BE(products) |
| Hess's law works because enthalpy is a state function, you can add step enthalpies to get the total. | |
5. Types of Enthalpy Change
| Type | Meaning |
|---|---|
| Enthalpy of formation | ΔH when 1 mole of a compound forms from its elements |
| Enthalpy of combustion | ΔH when 1 mole burns completely in oxygen (always −ve) |
| Enthalpy of neutralisation | ΔH when acid and base form 1 mole of water (≈ −57.1 kJ for strong acid-base) |
| Enthalpy of solution | ΔH when 1 mole of substance dissolves |
| Enthalpy of atomisation | ΔH to break 1 mole into gaseous atoms |
| Standard conditions are 298 K and 1 bar, shown with the ° symbol (ΔH°). | |
6. Entropy & Gibbs Free Energy
| Concept | Formula |
|---|---|
| Entropy change | ΔS = q_rev / T |
| Second law (spontaneity) | ΔS_universe > 0 for a spontaneous process |
| Gibbs free energy | ΔG = ΔH − TΔS |
| Gibbs and equilibrium constant | ΔG° = −2.303 RT log K |
| Spontaneity condition | ΔG < 0 spontaneous, ΔG = 0 equilibrium, ΔG > 0 non-spontaneous |
| Third law: the entropy of a perfectly crystalline substance is zero at absolute zero (0 K). | |
Spontaneity: Signs of ΔH, ΔS and ΔG
| ΔH | ΔS | ΔG | Spontaneous? |
|---|---|---|---|
| − | + | Always − | Yes, at all temperatures |
| + | − | Always + | No, at any temperature |
| − | − | − at low T | Yes, at low temperature |
| + | + | − at high T | Yes, at high temperature |
| Both enthalpy and entropy, together with temperature, decide whether a reaction is spontaneous. | |||
Worked Examples
| Problem | Solution |
|---|---|
| ΔU if q=+50 J, W=+30 J | ΔU = q + W = 50 + 30 = 80 J |
| ΔH, ΔU=80, Δn_g=1, T=300 | ΔH = 80 + (1)(8.314)(300) ≈ 2574 J |
| Work at const P, P=2, ΔV=3 | W = −PΔV = −2 × 3 = −6 (units) |
| ΔG, ΔH=−100, T=300, ΔS=0.2 | ΔG = −100 − 300(0.2) = −160 kJ |
| q, m=10, c=4.18, ΔT=5 | q = 10 × 4.18 × 5 = 209 J |
| Always keep track of signs and units, they are where most marks are lost in this chapter. | |
Common Mistakes to Avoid
- Sign errors: Heat given to system is +q, work done on system is +W (NCERT convention)
- ΔH vs ΔU: Use ΔH = ΔU + Δn_gRT, and count only gaseous moles in Δn_g
- State vs path function: U, H, S, G are state functions, q and W are not
- Spontaneity: ΔG decides spontaneity, not ΔH alone
- Standard conditions: The ° symbol means 298 K and 1 bar
Why This Chapter Matters for JEE & NEET
- High weightage: Thermodynamics appears every year in JEE Main, Advanced and NEET
- Formula heavy: Clear formulas make it a fast, scoring chapter
- Foundation for more: Links directly to equilibrium and electrochemistry in Class 12
- Concept plus numericals: Rewards students who understand signs and state functions
How to Use This Formula Sheet
- Fix the sign convention first: It prevents most silly errors
- Master ΔH = ΔU + Δn_gRT: A very common JEE and NEET formula
- Learn the spontaneity table: ΔH, ΔS and ΔG signs are frequently tested
- Revise from the PDF: Skim it before every chemistry test and mock
Get the Complete Formula Sheet PDF Free
Download the full Thermodynamics and Thermochemistry Class 11 formula sheet and revise anytime, anywhere.
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