Mass Spectrometry & Relative Mass
Relative atomic mass
Ar = Σ (isotope abundance × isotope mass) / Σ abundances Mass number A = protons + neutrons; isotopes have same Z, different A.
OCR A Level Chemistry A H432
🧪 OCR A Level Chemistry Formula Sheet 2026
Every essential equation, constant and rule for OCR A Level Chemistry A (H432) — moles, energetics, kinetics, equilibria, electrochemistry, organic mechanisms and analysis — for 2026 exams.
Physical Chemistry Inorganic & Energetics Organic Mechanisms H432 Specification
Our formula sheets are free to download — save this one as PDF for offline revision.
Aligned with the latest 2026 syllabus and board specifications. This sheet is prepared to match your exam board’s official specifications for the 2026 exam series.
All H432 Chemistry Equations and Mechanisms
OCR A Level Chemistry A (H432) is examined across three papers covering physical, inorganic and organic chemistry. This 2026 sheet collects every required equation, mechanism class and analytical technique into a single navigable reference.
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Moles, gas calculations and yield
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Energetics, Hess, Born-Haber and Gibbs
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Kinetics, equilibria, Ka, Kp and buffers
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Organic mechanisms and analytical techniques
Atomic Structure & Amount of Substance
Moles, gas calculations, yields and atom economy.
Moles
n = m / M (mass / molar mass) n = c V (concentration × volume in dm³) Ideal gas equation
pV = nRT with R = 8.31 J K⁻¹ mol⁻¹ ; p in Pa, V in m³, T in K Yield & Atom Economy
% yield
% yield = (actual moles / theoretical moles) × 100% % atom economy
% atom economy = (Mr of desired product / Σ Mr of all products) × 100% Bonding & Structure
Electronegativity, intermolecular forces, lattice enthalpy.
Bond Polarity
Polarity arises from electronegativity difference (Pauling scale, F = 4.0) Δχ < 0.4 → non-polar covalent ; 0.4–1.7 → polar covalent ; > 1.7 → ionic character Intermolecular Forces (weakest → strongest)
London dispersion (induced dipole-induced dipole) < permanent dipole-dipole < hydrogen bonding (N/O/F–H ⋯ N/O/F) Lattice Enthalpy
Lattice enthalpy ΔH_latt is exothermic for ionic compounds; magnitude increases with higher charge and smaller radius (∝ q₁q₂/r) Energetics & Entropy
Hess cycles, bond enthalpies, Born-Haber, entropy and Gibbs.
Enthalpy Change
Calorimetry
q = m c ΔT (for solutions, take m as mass of solution; c ≈ 4.18 J g⁻¹ K⁻¹ for water) Per mole
ΔH = q / n (with appropriate sign) Hess's Law
From formation enthalpies
ΔH_r = Σ ΔH_f(products) − Σ ΔH_f(reactants) From combustion enthalpies
ΔH_r = Σ ΔH_c(reactants) − Σ ΔH_c(products) From bond enthalpies
ΔH ≈ Σ bonds broken (reactants) − Σ bonds formed (products) Born-Haber Cycle (ionic compound formation)
ΔH_f(MX) = ΔH_at(M) + IE(M) + ΔH_at(X) + EA(X) + ΔH_latt(MX) Watch signs: ΔH_at and IE are endothermic; EA and ΔH_latt are typically exothermic.
Entropy & Gibbs Free Energy
Entropy change
ΔS_system = Σ S(products) − Σ S(reactants) (J K⁻¹ mol⁻¹) Gibbs free energy
ΔG = ΔH − T ΔS (T in kelvin; reaction feasible if ΔG < 0) Feasibility temperature
When ΔG = 0, T = ΔH/ΔS Kinetics
Rate equations, orders and the Arrhenius equation.
Rate Equation
rate = k [A]^m [B]^n where m, n are orders found experimentally Overall order
= m + n ; units of k depend on overall order Determining Order
Concentration-time graph: zero order → straight line, first order → constant t_½, second order → 1/[A] linear Rate-concentration graph: gradient gives k once orders identified Arrhenius Equation
k = A e^(−Ea/RT) Linear form
ln k = ln A − Ea/R × (1/T) (plot ln k vs 1/T, gradient = −Ea/R) Equilibria, pH & Buffers
Kc, Kp, Brønsted-Lowry acids and Henderson–Hasselbalch.
Equilibrium Constants
Kc
For aA + bB ⇌ cC + dD : Kc = [C]^c [D]^d / ([A]^a [B]^b) Kp
Kp = (P_C^c P_D^d)/(P_A^a P_B^b) where partial pressure P_i = x_i × P_total (x = mole fraction) Le Chatelier
Increase concentration of reactants → equilibrium shifts forwards ; increase pressure → shifts to side with fewer gas moles ; increase T → shifts in endothermic direction pH Calculations
pH = −log₁₀ [H⁺] ; [H⁺] = 10⁻ᵖᴴ Water
Kw = [H⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 298 K (so pure water pH = 7) Weak Acids
HA ⇌ H⁺ + A⁻ ; Ka = [H⁺][A⁻]/[HA] ; pKa = −log₁₀ Ka For weak monoprotic acid: [H⁺] ≈ √(Ka × [HA]_initial) Buffer Solutions
Henderson–Hasselbalch
pH = pKa + log₁₀ ([A⁻] / [HA]) Buffer resists pH change: weak acid + conjugate base, or weak base + conjugate acid.
Redox & Electrochemistry
Standard electrode potentials and Faraday's constant.
Oxidation Numbers & Half-Equations
Balance redox: balance atoms, balance O with H₂O, balance H with H⁺, balance charge with e⁻ ; combine half-equations cancelling e⁻ Standard Electrode Potentials
Cell EMF
E°_cell = E°_cathode (reduction) − E°_anode (reduction) E°_cell > 0 → reaction feasible under standard conditions; cathode is the more positive E°.
Faraday's Constant
F = 96 500 C mol⁻¹ (charge per mole of electrons) Charge passed
Q = It ; moles of electrons n_e = Q / F Organic Mechanisms
Functional groups and the four key mechanism types.
Nucleophilic Substitution (haloalkanes)
R–X + Nu⁻ → R–Nu + X⁻ Primary haloalkanes → SN2 (concerted) ; tertiary → SN1 (carbocation intermediate) Electrophilic Addition (alkenes)
C=C + H–X → CH–CX (proceeds via carbocation; Markovnikov: H adds to C with more Hs) Electrophilic Substitution (arenes)
Benzene + E⁺ → C₆H₅–E + H⁺ ; e.g. nitration with HNO₃/H₂SO₄ generates NO₂⁺ Free Radical Substitution (alkanes)
Initiation
X₂ → 2 X• (UV light) Propagation
X• + RH → HX + R• ; R• + X₂ → RX + X• Termination
Two radicals combine, e.g. R• + X• → RX Esterification & Polymerisation
Esterification
R–COOH + R'–OH ⇌ R–COO–R' + H₂O (acid catalyst) Addition polymerisation
n CH₂=CHR → −[CH₂–CHR]ₙ− Condensation polymerisation
Diol + dicarboxylic acid → polyester + n H₂O ; diamine + diacid → polyamide + n H₂O Analytical Techniques
NMR, IR and mass spectrometry interpretation.
¹H NMR (Proton)
Chemical shift δ (ppm) indicates environment ; integration ratio = ratio of H atoms ; (n + 1) rule for splitting TMS reference at δ = 0 ; use D₂O wash to identify O–H / N–H protons (they vanish).
¹³C NMR
Number of peaks = number of carbon environments ; chemical shift indicates type of carbon (e.g. C=O ≈ 170–220, aromatic ≈ 110–150, C–H sp³ ≈ 0–50) Infrared (IR)
O–H (alcohols) broad ≈ 3200–3600 cm⁻¹ ; C=O ≈ 1680–1750 cm⁻¹ ; C–H ≈ 2850–3100 cm⁻¹ ; O–H (carboxylic acid) very broad 2500–3300 cm⁻¹ Mass Spectrometry
Molecular ion
M⁺ peak = relative molecular mass Fragments
Loss of common groups: −15 (CH₃), −17 (OH), −29 (CHO/C₂H₅), −45 (COOH) How to Use This Formula Sheet
Boost your Cambridge exam confidence with these proven study strategies from our tutoring experts.
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Master the Mechanism Toolkit
Most organic questions test 4 mechanisms. Drill curly arrows, intermediates and products until you can draw any one from a clean slate.
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Practise Mole Calculations Daily
Mole/concentration/gas-volume questions appear on every paper. Five minutes of drilling per day builds reflex accuracy.
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Plot the Arrhenius Graph
ln k vs 1/T is a classic OCR question — practise extracting Ea from the gradient, including units.
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Combine NMR + IR + Mass Spec
Synoptic spectroscopy questions give all three; cross-reference to deduce structure rather than relying on a single technique.
Formula Sheet FAQ
Quick answers about this free PDF and how to use it for exam revision and active recall.
Is the OCR A Level Chemistry Formula Sheet 2026 free to download as a PDF?
Yes. This Tutopiya formula sheet is free to use and you can download it as a PDF from this page for offline revision. There is no payment or account required for the PDF download.
What Chemistry topics and equations does this formula sheet cover?
This page groups key Chemistry formulas in one place for revision. OCR A Level Chemistry A (H432) formula sheet for 2026: moles and gas calculations, energetics, kinetics, equilibria, pH and buffers, electrochemistry, organic mechanisms and analytical techniques. Always cross-check with your official syllabus and past papers for your exam session.
Can I use this instead of the official exam formula booklet in the exam?
No. In the exam you must follow only what your exam board allows in the hall—usually the official formula booklet or data sheet where provided. This page is a revision and teaching aid, not a replacement for board-issued materials.
Who is this formula sheet for (Upper Secondary)?
It is written for students preparing for assessments at Upper Secondary in Chemistry, including classroom revision, homework support, and independent study. Teachers and tutors can also share it as a quick reference.
How should I revise with this formula sheet?
Work through past paper questions, quote the correct formula before substituting values, and check units and notation every time. Pair this sheet with timed practice and mark schemes so you see how examiners expect working to be set out.
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This formula sheet aligns with OCR A Level Chemistry A (H432) for the 2026 exam series.
OCR provides a Data Sheet in the exam — check the latest specification to confirm which constants and tables are given.