Download clean, printable lists of the most common mistakes students make — so you can fix them before they cost marks.
Each sheet is aligned to its exam board and built from recurring student errors highlighted in examiner reports and mark schemes.
What you get
A topic-by-topic mistakes list with a “do this instead” fix and a quick self-check.
How to use it
Review before past papers, then use the quick checks to catch errors under timed conditions.
Why it works
Many marks are lost on predictable slips: rounding, sign errors, units, and misreading commands.
Coverage by topic
Preview (up to 5 per topic)
14 total rows in download
| Topic | Common mistake / misconception | Do this instead | Quick check |
|---|---|---|---|
| Atomic Structure | Confusing the Bohr model with the quantum mechanical model. | Bohr: electrons in fixed orbits. QM: electrons in orbitals (probability regions). IB DP uses QM model — atomic orbitals (s, p, d, f) with specific shapes. | IB DP: s (spherical), p (dumbbell), d (cloverleaf). Electrons in orbitals not orbits. |
| Atomic Structure | Writing incorrect electron configurations for transition metals. | 4s fills before 3d but 4s loses electrons first when ionised. e.g. Cu: [Ar]3d¹⁰4s¹ (exception). Cr: [Ar]3d⁵4s¹. | Check exceptions: Cu and Cr in Period 4. When forming ions, remove 4s first. |
| Bonding | Predicting molecular polarity from bond polarity alone. | A molecule with polar bonds may be non-polar overall if the vectors cancel (e.g. CO₂, CCl₄). Must consider molecular geometry using VSEPR. | Polar bonds + symmetrical shape = non-polar molecule (dipoles cancel). |
| Bonding | Confusing bond order and bond strength in resonance structures. | Resonance delocalises electrons. Average bond order between 1 and 2 (e.g. ozone: bond order 1.5). All equivalent bonds have same length and strength. | Resonance: average bond order. e.g. ozone has two identical O-O bonds (not alternating). |
| Energetics | Forgetting state symbols in enthalpy equations. | State symbols (s, l, g, aq) are ESSENTIAL in enthalpy equations and thermochemical definitions. Different states = different enthalpies. | Every substance in a thermochemical equation needs a state symbol. |
| Energetics | Confusing ΔG, ΔH and ΔS signs for spontaneity. | ΔG = ΔH − TΔS. Spontaneous when ΔG < 0. Can be spontaneous even with ΔH > 0 if TΔS is large enough. Check all combinations. | ΔG < 0 = spontaneous. ΔH − and ΔS + always spontaneous. Others depend on temperature. |
| Kinetics | Reading the rate order from the balanced equation. | Rate = k[A]^m[B]^n. Orders m and n are determined EXPERIMENTALLY. Stoichiometric coefficients are not orders. | Rate order: experiment only. Never from equation coefficients. |
| Kinetics | Confusing rate constant k with rate of reaction. | k is constant for a given temperature — it does not change with concentration. Rate = k[A]^m changes as [A] changes. | k changes only with temperature (Arrhenius). Rate changes with concentration. |
| Equilibrium | Saying Kc changes when concentration of a reactant changes. | Kc is ONLY affected by temperature. Adding/removing reactants or products changes Q and shifts equilibrium, but Kc stays constant (at constant T). | Kc: only temperature changes it. Concentration, pressure, catalyst → shift, not change Kc. |
| Acids and Bases | Saying a buffer works because it 'neutralises' acids or bases. | A buffer resists pH change by: weak acid reacting with added base (HA + OH⁻ → A⁻ + H₂O), and conjugate base reacting with added acid (A⁻ + H⁺ → HA). | Buffer = weak acid + conjugate base. Explain both reactions for added acid AND added base. |
| Acids and Bases | Confusing amphoteric and amphiprotic substances. | Amphiprotic: can donate or accept a proton (e.g. HCO₃⁻, H₂O). Amphoteric: can react as acid OR base — broader term including non-protic substances (e.g. Al₂O₃). | All amphiprotic substances are amphoteric. Not all amphoteric are amphiprotic. |
| Organic Chemistry | Confusing addition and substitution reactions for benzene. | Benzene undergoes ELECTROPHILIC SUBSTITUTION (not addition) because addition would destroy the stable delocalised ring. e.g. nitration, halogenation, Friedel-Crafts. | Benzene: EAS (electrophilic aromatic substitution). Alkenes: addition. |
| Organic Chemistry | Identifying chiral centres incorrectly. | A chiral centre = carbon bonded to FOUR DIFFERENT groups. Count the substituents. Even two H atoms make it non-chiral. | Count: four DIFFERENT groups on the carbon? If yes → chiral centre. |
| Option Topics | Writing about Haber process without evaluating the compromise conditions. | High pressure: more NH₃ (Le Chatelier) but expensive. Low temperature: more NH₃ but slower rate. Compromise: 450°C, 200 atm, iron catalyst. | Explain WHY the conditions are a compromise between yield and rate. |