Chem notes / Physical Chemistry

Physical Chemistry · 100% marks notes

Physical full marks = classify the numerical family in ≤15s, run a fixed equation set, and recognise multi-concept joins so most stems finish in 45–75 seconds.

Goal Bank ~45–50 /100 Chem (~full Physical share)Weight ~50% of Chemistry tags (2020–2026)Speed 45–75sShare 49.8%Trend Falling share

All Chem notes Physical Inorganic Organic

Jump to topicMole & Stoichiometry Gases & Liquids Atomic Structure Chemical Bonding Thermodynamics Chemical Equilibrium Ionic Equilibrium Electrochemistry Kinetics Solid, Solutions & Surface

Physical in Advanced is Mole/Gaseous, Thermo, Equilibrium, Electrochem, Kinetics, Solutions/Colligative, Solid/Surface, Atomic. Recent papers fuse chapters (thermo↔K, ionic↔conductance/Nernst). 100% means you never start from blank memory — you start from a named template, then check for a second-chapter join. Physical full marks are correct model choice under the clock.

Topic-wise on this page

Physical Chemistry · chapter details

Same content as each topic page — brief, paper asks, methods, formulas, and families — so you can study here first, then open a full topic only when you need samples or trends.

01 · A direct numerical bank and the calculation language beneath all Physical Chemistry

Mole Concept & Stoichiometry

Full topic page →

PromiseLock a basis, convert everything to moles or equivalents, identify the limiting event, and most mixed-composition or redox stems collapse in under 75 seconds.

Advanced rarely asks only Avogadro arithmetic. It hides stoichiometry inside purity, sequential reactions, mixtures, titration, oxidation number and concentration changes; one conserved basis keeps the chain controlled. Lock a 100 g or 1 L basis early; most mixture and titration stems become linear algebra, not chemistry theatre.

01. A balanced equation is a mole-ratio machine, not a mass-ratio statement. Convert first, react second, convert back last.

02. For mixtures, introduce minimum unknown mole variables and use independent balances: total mass, atoms, charge, gas volume or equivalents.

03. Concentration units are not interchangeable: molarity changes with temperature, while molality and mole fraction do not depend on solution volume.

How Advanced asks this

Impure reagent or multistep yield with a limiting reagent
Mixture composition from gas volume, mass change or combustion products
Molarity–molality–mole-fraction conversion using density
Back titration, disproportionation or mixed oxidant/reductant equivalents
Integer answer based on atoms, molecules, electrons or isotopic abundance

Traps that leak marks

Comparing reactant masses instead of n/ν
Using M₁V₁=M₂V₂ across a chemical reaction
Treating normality or n-factor as intrinsic
Using solution mass where solvent mass is required for molality
Applying percentage yield twice in a multistep chain
Comparing reactant masses instead of n/ν
Using M₁V₁=M₂V₂ across a chemical reaction
Applying yield and purity to the same step twice

Must cover (this topic)

Stoichiometry & concentration measures

60–90s process

0–12s — Choose a basis: 1 mol, 100 g, 1 L solution, or the amount actually given.
12–25s — Balance the reaction; write initial moles and stoichiometric requirements or electron change.
25–60s — Find min(available/ν), advance reaction extent, then apply purity, yield, dilution or concentration conversion.
60–75s — Verify atom/charge balance, non-negative leftovers, plausible composition and requested significant unit.

Methods that change the score

Stoichiometry becomes fast when every quantity is converted to moles or reaction extent before arithmetic.

Method 01 · Extent table

One ξ handles limiting reagent, leftovers and equilibrium-ready composition without verbal jumps.

Do this: Write initial/change/final moles as n_i,0+ν_iξ.

Method 02 · Hundred-gram basis

Percentages become masses immediately and unknown scale disappears.

Do this: For percentage composition or purity, assume 100 g unless another basis is cleaner.

Method 03 · Independent-balance mixture solve

Prevents redundant equations and exposes impossible mixture data.

Do this: Use only balances independent of the reaction equation.

Method 04 · Electron ledger

Works through unusual media and avoids memorised, reaction-independent n-factors.

Do this: Find oxidation-number change per formula unit, then equate electrons lost and gained.

Quick formulas

Amount and entities: n = m/M = N/N_A; N_A = 6.022×10²³ mol⁻¹ — Mass, particles and molar mass conversion
Reaction extent: n_i = n_i,0 + ν_i ξ; ξ_max = min(n_reactant,0/|ν|) — Limiting reagent and sequential reaction bookkeeping
Concentrations: M = n_solute/V_solution(L); m = n_solute/m_solvent(kg); x_i = n_i/Σn — Solutions and interconversion
Dilution: M₁V₁ = M₂V₂ (solute moles conserved) — Only solvent is added or removed
Normality/equivalents: N = M×n-factor; equivalents = N V(L); eq_oxidant = eq_reductant — Acid–base or redox titration in a specified reaction
Molarity from molality: M = 1000 d m/(1000 + mM_s), with d in g mL⁻¹ and M_s in g mol⁻¹ — Density links solution volume to solvent mass
Average molar mass: M̄ = Σx_i M_i; for gases, ρ = PM̄/RT — Gas mixtures or isotopic/molecular mixtures

Common question families

Limiting reagent and yield

Looks like: Mixed reactants, product mass or percentage yield

Fast model: Convert everything to reaction extents n/ν.

Mixture by independent reactions

Looks like: Impure sample or two components consuming one reagent

Fast model: Assign component moles and write only independent balances.

Equivalent and redox stoichiometry

Looks like: Oxidant–reductant, iodometry or equivalent mass

Fast model: Use electrons exchanged or n-factor equivalents.

Sequential gas or precipitate analysis

Looks like: Combustion products, absorption train or gravimetry

Fast model: Track conserved atoms through each measured product.

Sample preview · Limiting reagent and yield

10.0 mol N₂ and 24.0 mol H₂ react completely. Find NH₃ formed.

Answer: 16 mol NH₃

Use the minimum n/ν.

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02 · High-return numericals when state equations, partial pressures and molecular speeds stay separated

Gaseous & Liquid States

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PromiseIdentify ideal, mixture, kinetic-theory or real-gas mode in 12 seconds; then one state equation plus a physical limit check controls the stem.

The paper mixes macroscopic P–V–T data with molecular speeds and non-ideality. Never splice formulas from different models without checking whether pressure is total or partial and whether the same T and molar mass apply. Name the speed type before opening a formula sheet — most kinetic-theory errors are label errors, not algebra errors.

01. PV=nRT is a model whose strongest domain is low pressure and high temperature; van der Waals corrections explain finite molecular size (b) and attractions (a).

02. Dalton works with gas-phase partial pressures. Vapour collected over liquid requires subtracting that liquid's equilibrium vapour pressure.

03. Speed order is v_mp < v_avg < v_rms for one gas at one temperature; every characteristic speed scales as √(T/M). Diffusion/effusion follows Graham’s square-root mass law.

How Advanced asks this

Gas collected over water or reacting gas mixture
Density/molar-mass determination under non-STP conditions
Compare v_mp, v_avg, v_rms, kinetic energy or effusion rates
van der Waals constants, compressibility factor and limiting behaviour
Intermolecular-force effects on vapour pressure, boiling point, viscosity and surface tension

Traps that leak marks

Using total pressure for gas collected over water
Putting molar mass in g mol⁻¹ into SI speed formula
Assuming equal speeds because kinetic energies are equal
Calling every Z<1 gas ideal-like
Including condensed water in Dalton's gas total
Using wet-gas total pressure as dry P
Putting M in g mol⁻¹ into SI speed formulas
Assuming equal speeds because mean KE is equal

Must cover (this topic)

Zero/first order kinetics + Arrhenius

60–90s process

0–12s — Classify: ideal state, Dalton mixture, kinetic speed, effusion, real gas, or liquid-property trend.
12–25s — Write partial pressures/moles and choose PV=nRT, speed scaling, Graham, or van der Waals—not a hybrid.
25–60s — Solve in absolute temperature with consistent R units; use mole fractions before partial pressures.
60–75s — Check P,V,T limits, Σp_i=P, speed dimensions, and whether attractions should make Z below or above unity.

Methods that change the score

Gas and liquid questions are bookkeeping problems once partial pressure, molar volume and phase composition are separated.

Method 01 · Partial-pressure inventory

Dalton applies to what remains in the gas phase, not blindly to initial labels.

Do this: Convert each gas to moles, remove reacted/condensed species, then calculate p_i.

Method 02 · Ratio before constants

Cancels units and exposes √T/M scaling directly.

Do this: Divide two gas-state or speed equations before substituting R.

Method 03 · Z-sign diagnosis

Attraction lowers observed P (Z<1); hard-core repulsion dominates high P (Z>1).

Do this: At moderate P ask whether attraction or excluded volume dominates.

Method 04 · Property-force map

One causal map replaces disconnected memorisation.

Do this: Translate liquid trend to intermolecular forces before ranking.

Quick formulas

Ideal gas: PV=nRT; ρ=PM/RT — Dilute gas and molar-mass/density stems
Dalton law: P=Σp_i; p_i=x_iP=n_iRT/V — Non-reacting ideal-gas mixtures
Molecular speeds: v_mp=√(2RT/M); v_avg=√(8RT/πM); v_rms=√(3RT/M) — Speed comparison; M in kg mol⁻¹ for SI speed
Mean translational energy: Ē_trans=(3/2)RT per mole; (3/2)k_BT per molecule — Ideal-gas molecular energy at T
Graham law: r₁/r₂=√(M₂/M₁)=√(ρ₂/ρ₁) at same T,P — Effusion/diffusion comparison
van der Waals: (P+a n²/V²)(V−nb)=nRT — Attraction and excluded-volume corrections
Compressibility: Z=PV/(nRT); Z→1 as P→0 — Measure and direction of non-ideality
Clausius–Clapeyron: ln(P₂/P₁)=−ΔH_vap/R(1/T₂−1/T₁) — Approximate vapour-pressure change over a modest range

Common question families

Gas mixture and partial pressure

Looks like: Several gases mixed, collected over water or selectively removed

Fast model: Use mole bookkeeping with Dalton’s law.

Real-gas equation

Looks like: van der Waals constants, compression factor or critical data

Fast model: Insert molar volume consistently before interpreting deviation.

Kinetic theory and effusion

Looks like: RMS speed, temperature change or porous-wall escape

Fast model: Compare squared speeds or use Graham’s square-root ratio.

Liquid vapour and colligative behavior

Looks like: Vapour pressure, boiling point or nonvolatile solute

Fast model: Work with mole fraction and relative lowering.

Sample preview · Gas mixture and partial pressure

2 mol N₂ and 3 mol H₂ occupy a vessel at total pressure 10 bar. Find p(H₂).

Answer: 6 bar

Partial pressure follows mole fraction.

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03 · Reliable MC/NUM marks from spectrum, quantum-number and electronic-configuration logic

Atomic Structure

Full topic page →

PromiseSeparate hydrogen-like formulas from many-electron rules, then use quantum-number legality and energy ordering as fast option filters.

Atomic Structure has two models: exact one-electron results and qualitative many-electron orbital filling. Advanced distractors deliberately cross those boundaries. Configuration first, then anomaly — half-filled and filled subshells explain most IE and exception stems without memorising tables.

01. Bohr energies and radii are exact only for hydrogen-like one-electron species; nuclear charge enters as Z² in energy and 1/Z in radius.

02. A spectral line is an energy difference, not an orbital energy. Sign describes absorption/emission; wavelength depends on the magnitude.

03. Quantum numbers define allowed states: n sets shell, l subshell, m_l orientation and m_s spin. Counting follows from allowed integer values.

How Advanced asks this

Hydrogen-like transition wavelength, energy or series limit
de Broglie wavelength and accelerating potential
Allowed quantum-number sets and orbital/electron counts
Electronic configuration, unpaired electrons and magnetic character
Nodes, orbital shapes, penetration or energy-order statements

Traps that leak marks

Using Bohr formulas for a many-electron atom
Reversing wavelength and energy ratios
Taking uncertainty as equality in every situation
Using n+l ordering without Pauli/Hund
Removing d electrons before ns electrons when forming common transition-metal cations
Using Bohr formulas on many-electron atoms
Removing d electrons before ns when forming common cations
Reversing wavelength and energy ratios

Must cover (this topic)

Bohr model; H spectrum; de Broglie; uncertainty
H-atom QM picture: energies, quantum numbers, ψ and probability density (plots), s/p/d shapes
Aufbau, Pauli, Hund

60–90s process

0–12s — Decide one-electron spectrum, wave-particle, quantum-number legality, or many-electron configuration.
12–25s — Write Z, initial/final n or the (n,l,m_l,m_s) constraints; for filling write the orbital order.
25–60s — Use energy difference/counting/filling, preserving transition direction and Pauli–Hund occupancy.
60–75s — Check one-electron applicability, sign/order, degeneracy, electron count and known configuration exceptions.

Methods that change the score

Energy-level and quantum-number models prevent formula mixing and expose impossible options quickly.

Method 01 · Model boundary stamp

Prevents applying E_n∝−Z²/n² to screened multielectron atoms.

Do this: Write H-like or many-electron before touching energies.

Method 02 · Transition energy first

Avoids reversing levels or attaching wavelength to one level.

Do this: Calculate ΔE=E_final−E_initial, then infer absorption/emission and λ.

Method 03 · Quantum-number sieve

Illegal options die before any counting.

Do this: Test n, then l, then m_l, then m_s in that order.

Method 04 · Box configuration audit

Makes unpaired count, spin and Pauli violations visible.

Do this: Draw only the active subshell boxes and apply Hund before pairing.

Quick formulas

Bohr energy: E_n=−13.6 Z²/n² eV per electron — Hydrogen-like ion only
Bohr radius: r_n=a₀ n²/Z; a₀=52.9 pm — Hydrogen-like orbit radius
Rydberg relation: 1/λ=R Z²|1/n_f²−1/n_i²| — One-electron absorption/emission wavelength
Photon: E=hν=hc/λ; c=νλ — Radiation energy and wavelength
de Broglie: λ=h/p=h/(mv); electron through V: λ(Å)≈12.27/√V — Non-relativistic matter waves
Uncertainty: Δx Δp_x ≥ ħ/2 = h/(4π) — Lower bound on simultaneous position/momentum precision
Orbital counts: orbitals in subshell=2l+1; shell=n²; max electrons=2(2l+1), 2n² — State counting
Nodes: total=n−1; angular=l; radial=n−l−1 — Hydrogenic orbital node questions

Common question families

Hydrogenic transition

Looks like: Wavelength, frequency or line-series transition

Fast model: Use the difference of −13.6Z²/n² energies.

de Broglie and uncertainty

Looks like: Accelerated particle, wavelength or localization

Fast model: Convert voltage to momentum before using λ=h/p.

Quantum numbers and orbital count

Looks like: Allowed sets, electrons in subshells or nodes

Fast model: Enforce quantum-number ranges in order.

Electronic configuration and spectra

Looks like: Ion configuration, magnetic moment or anomalous filling

Fast model: Remove electrons from highest n first and count unpaired electrons.

Sample preview · Hydrogenic transition

Find the photon energy emitted for H transition n=3→2.

Answer: 1.89 eV

Use level differences, not a single-level energy.

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04 · A frequent multi-correct and matching cluster driven by electron counting and geometry

Chemical Bonding & Molecular Structure

Full topic page →

PromiseCount valence electrons, build domains or MO occupancy, then derive shape, polarity and magnetism instead of recalling isolated pictures.

Bonding questions reward a hierarchy: Lewis/resonance → formal charge → VSEPR → hybridisation and polarity, or AO electron count → MO bond order and magnetism. Geometry and hybridisation are consequences, not starting guesses. Bonding is the join language for inorganic trends: polarity, hydrolysis and lattice arguments all start from structure, not slogans.

01. VSEPR counts electron domains around a centre; lone pairs occupy more angular space and compress bond angles. Molecular shape omits lone-pair positions.

02. Hybridisation is a localized model useful for σ frameworks; π bonds use unhybridised orbitals and do not add VSEPR domains.

03. Molecular polarity is the vector sum of bond dipoles, so polar bonds can produce a nonpolar symmetric molecule.

How Advanced asks this

Shape, hybridisation and bond-angle ordering across related species
Formal charge, resonance and equivalent bond lengths
Dipole moment or hydrogen-bonding comparison
MO bond order, stability and magnetic nature up to Ne₂
Isoelectronic species or σ/π bond counting

Traps that leak marks

Equating electron geometry with molecular shape
Counting a π bond as an extra steric domain
Calling a symmetric molecule polar because its bonds are polar
Using one MO order for every B₂–Ne₂ species
Treating hydrogen bonding as any attraction involving hydrogen
Equating electron geometry with molecular shape
Counting a π bond as an extra VSEPR domain
Using one MO order for every diatomic without checking

Must cover (this topic)

Orbital overlap; covalent bond; hybridisation s/p/d
MO diagrams for homonuclear diatomics up to Ne₂; H-bond; polarity/dipole
VSEPR shapes: linear, angular, triangular, square planar, pyramidal, square pyramidal, TBP, tetrahedral, octahedral

60–90s process

0–12s — Count valence electrons/steric number or identify an MO species; note charge and odd-electron status.
12–25s — Draw the minimum Lewis/MO skeleton, place lone pairs, and choose electron-domain or MO ordering.
25–60s — Derive shape, hybridisation, formal charge, bond order, magnetism or net dipole from the model.
60–75s — Check octets/known exceptions, electron count, symmetry, equivalent resonance bonds and limiting bond order.

Methods that change the score

Electron counting followed by geometry or MO filling turns apparently descriptive questions into deterministic ones.

Method 01 · Electron-domain pipeline

Stops shape names from being matched to the wrong number of lone pairs.

Do this: Lewis count → central SN → electron geometry → molecular shape → hybridisation.

Method 02 · Symmetry cancellation test

Bond polarity alone cannot decide molecular polarity.

Do this: Draw bond-dipole arrows on the actual molecular geometry and add vectors.

Method 03 · MO occupancy ledger

Bond order and magnetism emerge together and ion changes are handled cleanly.

Do this: Write valence electron count and fill each MO before calculating BO.

Method 04 · Isoelectronic transfer

Transfers one configuration without confusing equal electrons with equal size.

Do this: For equal electron counts, compare nuclear charge and then occupancy-derived bond order/size.

Quick formulas

Formal charge: FC = V − L − B/2 — Compare Lewis/resonance contributors
Steric number: SN = σ bonds to centre + lone pairs on centre — Main-group electron geometry and hybridisation
VSEPR repulsion: LP–LP > LP–BP > BP–BP — Bond-angle distortions
MO bond order: BO=(N_b−N_ab)/2 — Diatomic stability and bond-length comparison
Magnetic criterion: unpaired MO electron(s) ⇒ paramagnetic — MO occupancy questions
Dipole moment: μ=q r; molecular μ=vector sum of bond moments — Polarity and geometry
Percent ionic character: % ionic≈(μ_observed/μ_ionic)×100 — Approximate bond-character numerical

Common question families

Lewis structure and formal charge

Looks like: Best canonical structure, octet exceptions or resonance

Fast model: Minimize formal-charge magnitude while respecting electron count.

VSEPR shape and hybridization

Looks like: Shape, bond angle or lone-pair comparison

Fast model: Count steric number; distinguish electron geometry from molecular shape.

MO bond order and magnetism

Looks like: Diatomic ion stability, bond length or magnetic character

Fast model: Fill the correct MO ordering and use (Nᵦ−Nₐ)/2.

Polarity and intermolecular forces

Looks like: Dipole moment, boiling point or hydrogen bonding

Fast model: Combine bond polarity vectorially using molecular symmetry.

Sample preview · VSEPR shape and hybridization

Predict the molecular shape of SF₄.

Answer: Seesaw

Name molecular shape after removing lone pairs.

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05 · Dense but systematic marks from sign discipline, state functions and thermochemical cycles

Chemical Thermodynamics

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PromiseDeclare system, sign convention and path/state-function status first; then energy, entropy and spontaneity questions become controlled balances.

Advanced thermodynamics is less about formula recall than consistency. Heat and work depend on path; U,H,S,G are state functions. A correct sign convention and reference cycle prevents most losses. When a stem pairs thermo with equilibrium, translate everything into Q, K and ΔG — one language, two chapter labels.

01. Using chemistry convention, ΔU=q+w and pressure–volume work on the system is w=−∫P_ext dV; expansion gives negative work.

02. At constant volume q_v=ΔU; at constant pressure with only PV work q_p=ΔH. Neither equality is universal without its conditions.

03. Hess's law works because enthalpy is a state function. Formation, combustion, bond-enthalpy and lattice cycles are alternative paths to one ΔH.

How Advanced asks this

Isothermal/adiabatic/reversible/irreversible ideal-gas paths
Hess cycle from formation, combustion or bond enthalpies
Entropy and temperature range for spontaneity
ΔG°, equilibrium constant or nonstandard ΔG
Born–Haber lattice-enthalpy cycle and sign matching

Traps that leak marks

Using w=−PΔV for a reversible path with changing pressure without integration
Taking q=ΔH for every process
Dropping Δn_g in ΔH−ΔU
Mixing J and kJ in T=ΔH/ΔS
Reversing lattice-enthalpy convention silently
Using w = −PΔV on a reversible path with changing P without integration
Dropping Δn_g or counting condensed phases as gas
Mixing J and kJ when solving T = ΔH/ΔS

Must cover (this topic)

Thermodynamics ΔG criteria

60–90s process

0–12s — Mark system, initial/final states, path constraints and chemistry sign convention.
12–25s — Choose first-law balance, Hess/Born–Haber cycle, entropy relation or Gibbs criterion.
25–60s — Execute symbolically with path-specific q,w and stoichiometric Δ values before numerical substitution.
60–75s — Check state-function independence, expansion/work sign, units per mole, and whether spontaneity was confused with speed.

Methods that change the score

State functions, signs and process constraints must be fixed before numbers are substituted.

Method 01 · Sign box

Fixes the physical sign before algebra obscures it.

Do this: Write expansion/compression and heat in/out before numbers.

Method 02 · State-versus-path split

Prevents treating heat and work as state functions.

Do this: Compute ΔU/ΔH from endpoints, then derive q or w using the specified path.

Method 03 · Coefficient ledger Hess cycle

Avoids hidden sign and stoichiometric multipliers.

Do this: Reverse/scale equations visibly and apply the same operations to ΔH.

Method 04 · Spontaneity quadrant

Determines all-T, no-T, high-T or low-T behaviour immediately.

Do this: Classify signs of ΔH and ΔS before solving ΔG=0.

Quick formulas

First law: ΔU=q+w; w_PV=−∫P_ext dV — Closed-system energy accounting, chemistry convention
Ideal-gas isothermal reversible work: w=−nRT ln(V₂/V₁)=−nRT ln(P₁/P₂) — Reversible isothermal ideal-gas path
Enthalpy relation: ΔH=ΔU+Δ(PV); ideal-gas reaction: ΔH=ΔU+Δn_g RT — Relating reaction U and H at same T
Calorimetry: q=mcΔT; q_cal=C_calΔT; q_system=−q_surroundings — Heat capacities and calorimeters
Reaction enthalpy: ΔH°_rxn=ΣνΔH°_f(products)−ΣνΔH°_f(reactants) — Standard formation data
Bond enthalpy estimate: ΔH≈ΣD(bonds broken)−ΣD(bonds formed) — Gas-phase average bond enthalpies
Entropy/Gibbs: ΔG=ΔH−TΔS; ΔS_univ=ΔS_sys+ΔS_surr — Spontaneity at fixed T,P or universe criterion
Free energy and composition: ΔG=ΔG°+RT ln Q; ΔG°=−RT ln K — Nonstandard direction and equilibrium

Common question families

Hess-law cycle

Looks like: Unknown reaction enthalpy from several equations

Fast model: Treat reactions as algebraic vectors.

Calorimetry and phase change

Looks like: Mixing, heating or latent heat in an insulated vessel

Fast model: Set total heat exchanged to zero with piecewise q.

Entropy and spontaneity

Looks like: Temperature range or feasibility from ΔH and ΔS

Fast model: Use ΔG=ΔH−TΔS with consistent units.

State-function differentials

Looks like: Relations among ΔU, ΔH, q and w

Fast model: Fix the chemistry sign convention before substitution.

Sample preview · State-function differentials

For an ideal-gas reaction at 300 K, ΔU=10.0 kJ mol⁻¹ and Δn_g=2. Find ΔH.

Answer: 15.0 kJ mol⁻¹

Keep Δn_g restricted to gases.

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06 · High-yield numericals — often paired with thermodynamics (ΔG°=−RT ln K) in Advanced multi-concept stems

Chemical Equilibrium

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PromiseWrite the balanced equilibrium expression, compare Q with K, and solve one extent table—direction and composition stop being guesswork, including thermo–equilibrium joins.

Equilibrium constants encode a particular balanced reaction at a particular temperature. Advanced stems exploit reversed/scaled equations, inert gas conditions, coupled equilibria, degree of dissociation and ΔG°/K links. Treat thermo and equilibrium as one language: Q, K and ΔG. Richer bank: treat every disturbance as a Q-vs-K audit — recompute activities after the change, leave K alone unless T changed, then decide direction. Coupled equilibria and α tables reward the same habit.

01. K uses activities; in standard idealized problems pure solids and liquids have activity one and are omitted, while gaseous or dissolved species remain.

02. Q has the same form as K but uses current composition. Q<K drives forward and Q>K drives reverse until Q=K.

03. Changing concentration, pressure or adding inert gas may shift composition, but K changes only with temperature.

How Advanced asks this

K_c/K_p from equilibrium composition or degree of dissociation
Direction prediction using Q
Reverse, multiply or add reactions and transform K
Pressure, volume, inert-gas or temperature perturbation
Coupled equilibria and ΔG° ↔ K thermodynamic join

Traps that leak marks

Including pure solid concentration in K
Using initial rather than equilibrium concentration
Forgetting powers follow stoichiometric coefficients
Claiming pressure changes K
Using total moles before dissociation to calculate mole fractions
Including pure solid concentration in K
Claiming pressure or a catalyst changes K
Using initial moles for mole fractions after dissociation

Must cover (this topic)

Ionic equilibrium buffers/Ksp

60–90s process

0–12s — Balance reaction and mark phases; identify current versus equilibrium data.
12–25s — Write Q/K expression, omit only pure solids/liquids, and set an extent or dissociation variable.
25–60s — Compare Q with K for direction, then solve the equilibrium table with physical-root constraints.
60–75s — Check K transformation, Δn_g, non-negative composition, temperature dependence and limiting α.

Methods that change the score

Extent tables and Q-versus-K reasoning handle both numerical equilibrium and disturbances with one framework.

Method 01 · Equation fingerprint

K is meaningless without coefficients; reversal and scaling then become automatic.

Do this: Write the exact balanced target reaction above every K.

Method 02 · Q-first direction

Handles mixed simultaneous changes without qualitative ambiguity.

Do this: Calculate Q from the present state before invoking Le Chatelier.

Method 03 · Extent with physical root

Quadratic equilibrium equations often contain one algebraic but impossible root.

Do this: Use n_i=n_i,0+ν_iξ and reject roots causing negative moles.

Method 04 · Inert-gas condition split

At constant V reacting-species partial pressures are unchanged; at constant P volume expands and Q may change.

Do this: Separate constant V from constant P before predicting shift.

Quick formulas

Equilibrium constant: K_c=Π[c_i]^{ν_i}; K_p=Π(p_i/p°)^{ν_i} (dimensionless activity form) — Balanced reaction with products positive ν
K_p–K_c: K_p=K_c(RT)^{Δn_g} — Ideal gases; Δn_g=gas product coefficients−gas reactant coefficients
Reaction quotient: Q<K forward; Q>K reverse; Q=K equilibrium — Predict spontaneous reaction direction
Reaction transformations: reverse: K⁻¹; multiply equation by n: Kⁿ; add equations: K_total=ΠK_i — Constructed/coupled reactions
Free energy: ΔG=RT ln(Q/K); ΔG°=−RT ln K — Direction and equilibrium thermodynamics
van 't Hoff: ln(K₂/K₁)=−ΔH°/R(1/T₂−1/T₁) — Approximate K change if ΔH° constant
Dissociation example: A⇌nB, starting 1 mol: n_A=1−α, n_B=nα, n_total=1+(n−1)α — Degree-of-dissociation pressure expressions

Common question families

Kc, Kp and reaction manipulation

Looks like: Reverse, multiply or add equilibrium reactions

Fast model: Transform K exactly as the chemical equation is transformed.

ICE-table composition

Looks like: Initial moles and equilibrium amount, pressure or dissociation

Fast model: Use one reaction extent in an ICE table.

Reaction quotient direction

Looks like: Mixture suddenly changed in pressure, volume or composition

Fast model: Compare the instantaneous Q with K.

Coupled equilibria and degree of dissociation

Looks like: Successive reactions or gaseous dissociation with total pressure

Fast model: Express all partial pressures through extent and total moles.

Sample preview · Kc, Kp and reaction manipulation

For N₂O₄⇌2NO₂, Kp=4. Find Kp for NO₂⇌½N₂O₄.

Answer: 0.5

Transform K with the equation.

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07 · A major Advanced discriminator — often joined with electrochemistry, Ksp and buffers in multi-concept stems

Ionic Equilibrium

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PromiseDo stoichiometric neutralisation first, equilibrium second; this ordering controls acids, buffers, hydrolysis, precipitation and Advanced joins with conductance/Nernst.

Most pH errors come from choosing a memorised formula before identifying the dominant chemistry. Strong species react essentially to completion; only the surviving weak system deserves an equilibrium expression. Advanced papers increasingly fuse ionic equilibrium with colligative i-factors, Faraday/Nernst cells and conductance-based solubility. Richer bank: when κ or a cell potential appears, convert to [ion] first — ionic equilibrium joins conductance and Nernst more often than chapter walls suggest.

01. Acid–base strength is equilibrium tendency, not concentration. A dilute strong acid and a concentrated weak acid cannot be ranked by labels alone.

02. Charge balance, mass balance and equilibrium constants are the universal fallback when shortcuts fail or multiple weak species coexist.

03. Buffers resist pH change because both conjugate partners are present; Henderson–Hasselbalch is an approximation after any strong reagent has reacted.

How Advanced asks this

pH after mixing strong/weak acids and bases
Buffer preparation, capacity and added strong acid/base
Salt hydrolysis and amphiprotic species
K_sp, selective precipitation and common-ion solubility
Indicator/range or acid–base theory statement clusters
Multi-concept: K_sp from conductance, or pH from cell potential

Traps that leak marks

Applying Henderson before neutralising added strong acid/base
Assuming every equivalence point has pH 7
Using √(K_aC) despite a strong common ion
Writing K_sp=s² for every salt
Comparing K_sp values alone when salt stoichiometries differ
Applying Henderson before neutralising added strong acid/base
Assuming every equivalence point has pH 7
Writing K_sp = s² for every salt stoichiometry

Must cover (this topic)

Ionic equilibrium buffers/Ksp

60–90s process

0–12s — Inventory acid/base/ions in moles; label strong, weak, salt, buffer or sparingly soluble solid.
12–25s — Complete dominant stoichiometric neutralisation/precipitation first; identify the species left.
25–60s — Apply the correct equilibrium approximation or balances, then calculate pH, hydrolysis or solubility.
60–75s — Verify approximation size, charge/mass sense, pH range, Q_sp versus K_sp and common-ion powers.

Methods that change the score

The main speed gain is doing stoichiometry before equilibrium and selecting the dominant species.

Method 01 · Reaction before equilibrium

Equilibrium formulas applied before neutralisation model species that no longer coexist.

Do this: Use mole stoichiometry for strong acid/base, then classify leftovers.

Method 02 · Dominant-species map

Reduces crowded ionic systems to the equilibrium that controls pH.

Do this: Write the two or three species with appreciable concentration before equations.

Method 03 · Charge-balance fallback

It is exact and reveals neglected ions.

Do this: When shortcuts collide, combine electroneutrality, mass balance, K and K_w.

Method 04 · Q_sp precipitation gate

K_sp equality describes saturation, not every mixture.

Do this: Calculate post-mixing ion concentrations and Q_sp before using K_sp equality.

Quick formulas

Water and pH: K_w=[H⁺][OH⁻]=10⁻¹⁴ at 25 °C; pH+pOH=14 — Aqueous solutions at 25 °C unless another K_w is given
Weak acid/base: K_a=[H⁺][A⁻]/[HA]; K_b=[BH⁺][OH⁻]/[B] — Equilibrium after stoichiometry
Conjugate pair: K_a K_b=K_w; pK_a+pK_b=pK_w — Conjugate acid–base relation
Weak monoprotic estimate: [H⁺]≈√(K_a C), α≈√(K_a/C) — K_a≪C and no significant common ion
Buffer: pH=pK_a+log([A⁻]/[HA]) — Acidic buffer after strong reagent stoichiometry
Basic buffer: pOH=pK_b+log([BH⁺]/[B]) — Weak base/conjugate-acid buffer
Solubility product: A_mB_n(s)⇌mA+nB: K_sp=[A]^m[B]^n — Saturation, precipitation and molar solubility
Amphiprotic salt estimate: pH≈½(pK_a1+pK_a2) — Intermediate amphiprotic species such as HA⁻ under suitable dilution

Common question families

Buffer and common ion

Looks like: Weak acid/base with its salt or partial neutralization

Fast model: Do stoichiometry first, equilibrium second.

Polyprotic acid or amphiprotic ion

Looks like: Multiple Ka values, bicarbonate-like species

Fast model: Use dominance and charge balance instead of solving every equilibrium.

Solubility product

Looks like: Precipitation, selective separation or molar solubility

Fast model: Build Qsp from post-mixing concentrations.

Titration-region pH

Looks like: pH before, at or after equivalence

Fast model: Classify the region before choosing an equation.

Sample preview · Buffer and common ion

Find pH of equimolar CH₃COOH/CH₃COONa; Ka=1.8×10⁻⁵.

Answer: 4.74

An equimolar buffer has pH=pKa.

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08 · High-yield Advanced unit: multi-step Nernst, Faraday, conductance–solubility joins, batteries and corrosion

Electrochemistry

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PromiseBalance electrons, lock the cell reaction and Q, then Nernst, Faraday and conductance become controlled substitutions — including Advanced joins with Ksp and ionic equilibrium.

Advanced electrochemistry rarely stays in one formula. Stems fuse galvanic cells with thermodynamics, electrolysis with competing aqueous discharge, and molar conductivity with Kohlrausch, weak-electrolyte α, or sparingly soluble salt solubility. Primary/secondary batteries, fuel cells and corrosion sit on the same anode–cathode logic. Richer bank: series electrolysis, concentration cells, fuel-cell/corrosion half-processes and κ→S→K_sp joins are the same AnOx/RedCat ledger with different outputs — practise the ledger, not isolated formulas.

01. Oxidation always occurs at the anode and reduction at the cathode. In a galvanic cell the anode is negative; in an electrolytic cell an external source reverses electrode polarity labels, not the AnOx/RedCat definitions.

02. Standard reduction potentials combine as E°_cell=E°_cathode−E°_anode. Potentials are intensive — never multiply E° by stoichiometric coefficients when balancing electrons.

03. Nernst uses Q for the balanced cell reaction. Pure solids/liquids are omitted. Concentration cells are Nernst with E°=0 and Q fixed by the activity ratio of the same couple.

How Advanced asks this

Cell notation, spontaneous direction and E under nonstandard conditions
Concentration cell or pH from electrode potential
Electrolysis mass, gas volume, time or competing aqueous discharge
Conductivity, cell constant, Kohlrausch and Λ_m vs √c for strong electrolytes
Solubility of sparingly soluble salts from κ and Λ_m° (ionic + electrochemistry join)
Primary/secondary batteries, fuel cells and corrosion prevention

Traps that leak marks

Reversing Q in Nernst
Multiplying electrode potential by stoichiometric coefficient
Confusing electron moles with product moles
Calling the galvanic anode positive
Mixing S m⁻¹/S cm⁻¹ and concentration units
Using finite-c Λ_m instead of Λ_m° for sparingly soluble salts
Ignoring competing H₂O discharge in aqueous electrolysis
Reversing Q in Nernst
Calling the galvanic anode positive
Using finite-c Λ_m instead of Λ_m° for sparingly soluble salts

Must cover (this topic)

Nernst + conductance

60–90s process

0–12s — Write oxidation and reduction half-reactions; mark anode/cathode and electron count n. Note if the stem also asks conductance or solubility.
12–25s — Add to the balanced cell reaction, write Q and choose E°, Nernst, ΔG, Faraday or conductance/Kohlrausch model — or the κ–S join.
25–60s — Calculate without multiplying electrode potentials; convert current×time to charge; keep one unit system for κ and Λ_m.
60–75s — Check spontaneous sign, Q orientation, electron stoichiometry, deposited mass, dilution trend and that solubility used Λ_m° not an arbitrary Λ_m.

Methods that change the score

Advanced electrochemistry joins half-cells with thermodynamics, Faraday stoichiometry, and Kohlrausch–solubility reasoning — lock the balanced reaction and unit system first.

Method 01 · Half-reaction ledger

Fixes n and Q simultaneously, which controls Nernst and Faraday work.

Do this: Balance atoms, charge and electrons separately, then add.

Method 02 · Reduction-potential subtraction

Avoids double-negating an oxidation potential.

Do this: Keep table values as reductions and subtract anode from cathode.

Method 03 · Electron-mole bridge

One bridge handles metals, gases and simultaneous products.

Do this: Convert charge to mol e⁻ first, then use half-reaction stoichiometry.

Method 04 · Unit-system lock for conductance

Prevents the recurring 1000 or 10⁴ conversion error.

Do this: Write κ and length-area units before calculating Λ_m; for sparingly soluble salts use Λ_m°.

Quick formulas

Cell potential: E°_cell=E°_cathode(red)−E°_anode(red) — Both tabulated as standard reduction potentials
Nernst equation: E=E°−(RT/nF)ln Q = E°−(0.05916/n)log Q at 298 K — Balanced cell reaction under nonstandard conditions
Electrochemical thermodynamics: ΔG=−nFE; ΔG°=−nFE°=−RT ln K — Spontaneity and equilibrium constant
Faraday law: m=(It/F)(M/z); Q_charge=It; 1 F≈96485 C mol⁻¹ e⁻ — Electrolysis deposition or liberation
Conductance: G=1/R; κ=G(l/A)=G×cell constant — Convert measured resistance to conductivity
Molar conductivity: Λ_m=1000κ/c when κ is in S cm⁻¹ and c in mol L⁻¹; in SI, Λ_m=κ/c with c in mol m⁻³ — Normalize conductivity while keeping one unit system
Kohlrausch law: Λ_m°=Σν_i λ_i° — Limiting molar conductivity of electrolyte
Strong-electrolyte dilution: Λ_m ≈ Λ_m° − b√c (dilute range) — Extrapolate Λ_m° from Λ_m vs √c; b depends on electrolyte type
Weak-electrolyte dissociation: α=Λ_m/Λ_m°; K_a=cα²/(1−α) — Conductometric weak-electrolyte calculation
Sparingly soluble salt: κ ≈ Λ_m° × S (consistent units); then K_sp from dissolution stoichiometry — Advanced join of conductance with ionic equilibrium

Common question families

Cell potential and Nernst equation

Looks like: Nonstandard galvanic cell, concentration cell or equilibrium

Fast model: Write the balanced net reaction before Q.

Electrolysis and Faraday law

Looks like: Deposited mass, gas volume or series cells

Fast model: Convert charge to electron moles once.

Conductance and molar conductivity

Looks like: Cell constant, dilution or weak-electrolyte dissociation

Fast model: Separate measured conductance from conductivity and molar conductivity.

Electrochemical thermodynamics

Looks like: K, ΔG° and E° interconversion

Fast model: Use one balanced electron count across all relations.

Sample preview · Electrochemical thermodynamics

A cell has E°=0.0591 V at 298 K and n=1. Find K.

Answer: 10

The balanced electron count links E° and K.

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09 · Fast marks from rate-data ratios, integrated-law fingerprints and Arrhenius plots

Chemical Kinetics

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PromiseInfer order from evidence rather than coefficients, select the matching integrated law, and reserve mechanism claims for elementary steps.

Kinetics asks how fast and by what rate law—not whether a reaction is thermodynamically favourable. Experimental orders can be zero, fractional or negative and need not match overall stoichiometry. Richer bank: initial-rate ratios, fraction-remaining wording, and slow-step/pre-equilibrium mechanisms all ask the same question — what evidence fixes the rate law? Answer that before algebra.

01. Rate is normalized by stoichiometric coefficients so every species reports one reaction rate. Reactant concentration decreases, hence the minus sign.

02. The differential rate law is empirical unless an elementary step is specified. Molecularity belongs only to an elementary step and is a positive integer.

03. Integrated laws, half-life dependence and linear plots are three fingerprints of order; use all available evidence for consistency.

How Advanced asks this

Determine order and k from initial-rate data
Concentration/time, half-life or completion-fraction numerical
Identify linear plot and units of k
Arrhenius two-temperature or activation-energy calculation
Mechanism, slow step, steady-state/pre-equilibrium or catalyst statements

Traps that leak marks

Reading order directly from overall coefficients
Using first-order 2.303 log formula with natural log unchanged
Forgetting k units reveal overall order
Calling fractional order a molecularity
Claiming a catalyst shifts equilibrium
Reading order from overall coefficients
Mixing log₁₀ and ln in first-order formulas
Claiming a catalyst shifts equilibrium composition

Must cover (this topic)

Zero/first order kinetics + Arrhenius

60–90s process

0–12s — Identify data type: initial rates, concentration-time, half-life, Arrhenius or mechanism.
12–25s — Write rate=k[A]^m[B]^n or the candidate integrated law; state assumptions for any elementary step.
25–60s — Use ratios/linear form, solve order and k, then compute requested time, concentration or E_a.
60–75s — Check k units, positive concentrations, half-life dependence, temperature trend and distinction from equilibrium.

Methods that change the score

Order recognition determines the correct graph, half-life expression, units and integrated law.

Method 01 · Initial-rate ratio

Isolates one exponent without solving a simultaneous logarithmic system.

Do this: Choose two experiments where all but one concentration are unchanged.

Method 02 · Fingerprint triangle

A single noisy clue can mislead; three consistent signatures identify order.

Do this: Cross-check integrated plot, k units and half-life dependence.

Method 03 · Fraction remaining variable

Turns percent-completion wording into a clean logarithm or reciprocal.

Do this: Set [A]_t=f[A]_0 before using the integrated law.

Method 04 · Mechanism rate-law discipline

Prevents deriving an unsupported rate law from the overall equation.

Do this: Use stoichiometric powers only for an elementary rate-determining step, eliminating intermediates when needed.

Quick formulas

Stoichiometric rate: r=−(1/a)d[A]/dt=(1/p)d[P]/dt — aA→pP reaction-rate relation
Zero order: [A]_t=[A]_0−kt; t₁/₂=[A]_0/(2k) — Rate independent of A over stated range
First order: ln([A]_0/[A]_t)=kt; t₁/₂=ln2/k — First-order decay
Second order, one reactant: 1/[A]_t−1/[A]_0=kt; t₁/₂=1/(k[A]_0) — Rate=k[A]²
k dimensions: [k]=(concentration)^(1−n) time⁻¹ for overall order n — Order/unit checks
Arrhenius: k=Ae^(−E_a/RT); ln k=ln A−E_a/(RT) — Temperature dependence
Two-temperature Arrhenius: ln(k₂/k₁)=−E_a/R(1/T₂−1/T₁) — Find E_a or rate-constant ratio
Pseudo-first order: rate=k[A][B]^m=k'[A] when [B]≈constant in large excess — One reactant buffered/in excess

Common question families

Integrated rate-law identification

Looks like: Concentration or pressure data versus time

Fast model: Test the linear form or constant half-life signature.

Initial-rate method

Looks like: Several experiments with changed concentrations

Fast model: Divide rate equations pairwise.

Arrhenius comparison

Looks like: Rate constants at two temperatures or catalyst effect

Fast model: Use the logarithmic two-temperature form.

Mechanism and steady state

Looks like: Elementary steps, intermediate or observed rate law

Fast model: Eliminate intermediates using pre-equilibrium or steady state.

Sample preview · Integrated rate-law identification

A reactant falls from 0.80 M to 0.40 M in 20 min and to 0.20 M in 40 min. Identify order.

Answer: First order

Equal successive half-lives diagnose first order.

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10 · Three compact scoring units: crystal counting, solution deviations and adsorption/colloid logic

Solid State, Solutions & Surface Chemistry

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PromiseUse unit-cell ownership, solvent chemical-potential lowering and surface coverage as three separate models; mixed statement sets then become fast audits.

This combined syllabus block is broad but patterned. Solid state is geometry plus counting; solutions are vapour-pressure and particle-number thermodynamics; surface chemistry is adsorption and colloidal stability. When a stem mixes freezing-point depression with ionic equilibrium, fix i from the actual dissociated species — not from a memorised salt label.

01. Crystal questions require fractional ownership: corner 1/8, face 1/2, edge 1/4, body centre 1. The seven crystal systems (a,b,c,α,β,γ) fix the lattice type; packing questions usually focus on cubic and hexagonal close packing.

02. Point defects must preserve the stated charge and stoichiometry. Schottky lowers density; Frenkel relocates ions and approximately preserves density. Radius-ratio rules guide coordination in ionic solids when the stem invites that check.

03. Raoult's law defines ideal-solution behaviour. Colligative properties depend on solute particle count, so van't Hoff factor diagnoses association or dissociation — a frequent Advanced numerical.

How Advanced asks this

fcc/bcc/hcp atom count, coordination, packing or density
Crystal-system parameters and radius-ratio / nearest-neighbour logic
Schottky/Frenkel/non-stoichiometric defect statements
Raoult/Henry vapour-pressure and azeotrope/deviation trends
Colligative molar mass with association/dissociation and i
Freundlich adsorption, colloid charge, coagulation, emulsions/micelles

Traps that leak marks

Using a in pm directly with g cm⁻³ density
Confusing atoms per cell with coordination number
Assuming every solution obeys Raoult at all composition
Using i=M_observed/M_normal instead of the inverse relation implicit in colligative data
Extending Freundlich to saturation pressure where it cannot level off
Calling every colloidal system an emulsion
Using formula moles without the i-factor
Confusing packing fraction with density formula inputs
Treating every adsorption as monolayer Langmuir without stem cues

Must cover (this topic)

Colligative + packing fractions

60–90s process

0–12s — Tag the subtopic: unit-cell geometry, defect, vapour/solution equilibrium, colligative particles, adsorption or colloid.
12–25s — Draw one cell/particle inventory or write the correct pressure/property/adsorption relation with assumptions.
25–60s — Count ownership or particles first, then solve geometry, composition, molar mass, i or adsorption dependence.
60–75s — Check packing/coordination limits, charge neutrality, ideal/dilute assumptions, i direction and adsorption saturation sense.

Methods that change the score

Unit discipline and particle bookkeeping connect crystal, solution and surface questions.

Method 01 · Ownership table

Prevents memorised Z from failing on decorated or ionic cells.

Do this: Count each lattice site by its shared fraction before using Z.

Method 02 · Contact-line sketch

Derives a–r relations instead of swapping fcc and bcc formulas.

Do this: Draw the face/body diagonal where spheres touch and apply Pythagoras.

Method 03 · Particle-count solution model

Separates thermodynamic measurement from association/dissociation stoichiometry.

Do this: Convert solute chemistry to effective particle moles through i before colligative formulas.

Method 04 · Deviation interaction test

Predicts sign of Raoult deviation and azeotrope tendency causally.

Do this: Compare A–B attractions with A–A and B–B before ranking vapour pressure.

Quick formulas

Unit-cell density: ρ=Z M/(N_A a³) — Cubic cell with edge a and Z formula units per cell
Cubic contact geometry: sc: a=2r, Z=1; bcc: √3a=4r, Z=2; fcc: √2a=4r, Z=4 — Monatomic cubic packing
Packing/coordination: sc: 52.4%, CN6; bcc: 68.0%, CN8; fcc/hcp: 74.0%, CN12 — Standard close-packing comparison
Raoult law: p_i=x_i p_i°; P=Σx_i p_i° — Ideal volatile-liquid solution
Henry law: p=K_H x (common convention) — Dilute gas dissolved in liquid; use stated convention
Colligative properties: ΔT_b=iK_bm; ΔT_f=iK_fm; π=iCRT; relative lowering=(p°−p)/p°=x_solute — Dilute solution particle-count effects
van't Hoff factor: i=observed colligative property/calculated; dissociation to ν particles: i=1+(ν−1)α; dimerisation: i=1−α/2 — Association/dissociation
Freundlich isotherm: x/m=kP^(1/n); log(x/m)=log k+(1/n)log P, 0<1/n<1 — Empirical adsorption over moderate pressure range

Common question families

Crystal density and unit cell

Looks like: Edge length, density, Z or molar mass

Fast model: Use ρ=ZM/(a³Nₐ) with one unit system.

Defects and stoichiometry

Looks like: Vacancies, interstitials or aliovalent doping

Fast model: Enforce charge neutrality per formula unit.

Colligative molar mass

Looks like: Association/dissociation, freezing or osmotic data

Fast model: Extract van’t Hoff factor before molar mass.

Adsorption and colloids

Looks like: Freundlich isotherm, coagulation or micelles

Fast model: Identify the governing empirical law or charge rule.

Sample preview · Crystal density and unit cell

An fcc metal has edge 400 pm and molar mass 64 g mol⁻¹. Find density.

Answer: 6.64 g cm⁻³

Convert edge length before cubing.

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Open full Solid, Solutions & Surface notes (samples · trends · joins) →

Read first

How to use these notes for 100%

Point 01

Depth upgrade: Physical Chemistry is model selection — mole bookkeeping, equilibrium quotient, electrochemical cell map, or rate law — before plugging numbers.

Point 02

Bonding sits on the Physical↔Inorganic join: hybridisation/VSEPR language must stay consistent when Inorganic trends ask structure.

Speed system

45–75 second answer protocol

Use this on every stem — SC, MC, NUM, MATCH.

0
0–12s — Name the family: Mole-Gas / Thermo / Eqm / Electro / Kinetics / Solutions / Solid-Surface / Atomic. Circle units and what is asked (ΔU, K, E_cell, t½, Π, …).
12
12–25s — Write the governing equation(s) only — no story. State assumptions (ideal gas, reversible?, T fixed?, order).
25
25–60s — Plug numbers carefully (R, F, n, concentrations). For MC: compute once, then check each option as T/F against that value/relation.
60
60–75s — Unit/sign sanity (ΔG sign, E vs spontaneity, rate units, i≥1). Bubble and leave — do not re-derive.

Each statement is a separate check against your governing equation — never force consistency with another option.

Why it saves time

Protects partial marks; matching stays clean.

Instant recall

Mental bank

Keep these cold — no derivation during the 45–75s window.

Ideal gas: PV=nRT; remember R in the unit you need
First law: ΔU = q + w (use the paper’s sign convention consistently)
Isothermal reversible ideal gas: w = −nRT ln(V₂/V₁)
ΔG° = −RT ln K; spontaneity ↔ ΔG (not ΔG° alone for non-standard)
Nernst (25°C): E = E° − (0.059/n) log Q
First order: t½ = ln2 / k; zero order: t½ = [A]₀/(2k)
π = iCRT (osmotic); ΔTb = i Kb m; ΔTf = i Kf m
Kohlrausch: Λ°m = ν₊λ°₊ + ν₋λ°₋
Write the model (mole / K / cell / rate) in one line first
ΔG° = −RT ln K links thermo to equilibrium
Nernst needs reaction as written (electrons included)

Inside Physical

Sub-portion playbooks

Each family has a trigger, template, and drill.

01 · Base numerical

Mole concept · Gaseous state

45s triggerSee stoichiometry/P-V-T/mixture → mole table + gas law.

Template (write on rough)

Balance / find limiting reagent if reaction.
Convert to moles; apply PV=nRT or Dalton as needed.
Watch units of R and pressure.
MC: check each claim with the same mole table.

Must automate

Limiting reagent in ≤20s
Mole fraction ↔ partial pressure
rms / most probable relations with T when asked

Traps

Using wrong R units
Forgetting limiting reagent in multi-reactant stems

Drill

Daily: 1 stoichiometry NUM + 1 gas NUM

02 · High every-year

Chemical thermodynamics

45s triggerSee w, q, ΔU, ΔH, ΔG, Hess → path label first.

Template (write on rough)

Identify state functions vs path functions.
Label the path; write correct w and q.
Use Hess / cycle if formation data given.
For spontaneity: compute/interpret ΔG with the right standard vs non-standard.

Must automate

Irreversible vs reversible work
ΔH = ΔU + Δngas RT (ideal, const T) when applicable
Hess cycles without expanding everything

Traps

Sign convention flips mid-solution
Using ΔG° to judge a non-standard mixture

Drill

Daily: 1 work/ΔU NUM + 1 ΔG/K relation

03 · High

Chemical & ionic equilibrium

45s triggerSee K, buffer, Ksp, hydrolysis → write K expression / ICE.

Template (write on rough)

Write balanced reaction and Kp or Kc.
Compare Q and K if shift asked.
ICE only with clear initial amounts; watch dilution.
Buffers: Henderson with correct acid/base pair.

Must automate

Kp–Kc relation
Common ion effect on solubility
Buffer pH estimate

Traps

Wrong solids/liquids in K expression
Using Ka for the wrong species in buffer

Drill

Daily: 1 Kp/Kc + 1 buffer/Ksp

04 · High

Electrochemistry · Kinetics

45s triggerSee cell/E/Λ or rate/half-life → n-count or order first.

Template (write on rough)

Electro: cell reaction → n → Nernst / Faraday as asked.
Conductance: relate κ, G, Λm; Kohlrausch for weak electrolytes.
Kinetics: determine order from data → integrated law.
Arrhenius: ln k vs 1/T only after k values are consistent.

Must automate

0.059/n log form at 25°C
Faraday mass/volume relations
Zero vs first order signatures

Traps

Wrong n in Nernst
Calling a reaction first order from one half-life without check

Drill

Alt days: electro NUM / kinetics NUM

05 · Medium–High

Solutions · Solid state · Surface

45s triggerSee colligative/packing/adsorption → i-factor or lattice count.

Template (write on rough)

Colligative: identify i; use molality correctly.
Vapour: Raoult/Henry as applicable.
Solid: Z_eff for fcc/bcc/hcp; packing fraction.
Surface: physisorption vs chemisorption definitions; Freundlich form if numerical.

Must automate

i for electrolytes (ideal)
fcc Z=4, bcc Z=2 packing fractions
Relation between a and r for cubic lattices

Traps

Using molarity where molality is required
Wrong Z for lattice type

Drill

Weekly: 2 colligative + 1 packing

Habit

Common practice system

Same system every week — builds transferable speed.

Daily

25 min: 4 Physical NUM/SC from different families — each must show family name by 12s.
After each: write which universal method you used (Path / Q vs K / Nernst / Order / One-basis).
Redo any stem where equation choice happened after 25s.

Weekly

1 mixed Physical multi-correct with independent T/F.
1 electrochem + kinetics paired set timed (8 questions).
Error log: sign errors, wrong n, wrong R — write anti-trap lines.

Before every mock

Flash mental bank (Nernst, t½, colligative, packing) — 7 minutes.
In paper: clear easy Physical NUM early to bank marks under time.

Full marks gate

100% checklist for Physical Chemistry

Tick these only when true on timed practice — not when “you know the chapter”.

I name the Physical family in ≤12s on past papers.
Thermo always starts with path label.
Equilibrium always writes K (and Q if shift).
Electrochem always counts n before Nernst.
Kinetics always decides order before integrating.
Colligative always states i and concentration basis.
Zero guessed MC ticks — each option checked against the equation.
Equilibrium stems show Q vs K before Le Chatelier talk.
Kinetics: order from data, not from stoichiometry guess.

Paper coverage for Physical Syllabus map Subject analysis Chemistry · 300 plan

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