AP Chemistry FRQ Taxonomy, 2021–2026
Companion to frq_registry.json (245 per-part records). Sources: College Board FRQ booklets + scoring guidelines (SGs) in this directory. 2022 booklet is missing; question content reconstructed from 2022/ap22-sg-chemistry.txt + the per-part descriptions in 2022/ap22-cr-report-chemistry.txt. 2026 has no SG yet (points recorded as null).
Part labels are normalized to lowercase (a, b.ii, …) even for the digital-era exams (2025–2026) that print Part A / i. labels. 2026 Q2, Q3, Q6 are marked "Version J" (digital multi-version administration); the registry records the published version.
(a) Exam anatomy
- Section II: 1 h 45 min, 7 questions, 46 points (50% of exam score).
- Q1–Q3 "long": 10 points each, ~23 min each. Multi-part (8–10 scoreable parts), built around one scenario (usually a lab investigation or a substance system) and deliberately span 3–5 CED units.
- Q4–Q7 "short": 4 points each, ~9 min each. 3–4 parts, usually 1–2 units.
- Nearly every part is worth 1 point; 2-point parts are almost always two chained calculation steps (e.g., mass-by-difference → moles; q → ΔH; mol e⁻ → seconds) or claim + justification scored separately. 3-point parts are rare (2022 Q3d particulate diagram; 2022 Q2c, 2023 Q2c, 2024 Q5b, 2022 Q7b as multi-subpart clusters).
- Since 2023, sub-parts are labeled explicitly (i, ii, iii) and scored 1 point each; SGs emphasize consistency credit ("consistent with part (x)") — errors propagate without double penalty.
- 2025+ (digital): calculator + reference sheet in-app; "Show the work that leads to your answer" appears on virtually every calculation part.
- Every year 2021–2025 sums to exactly 46 points (verified; no SG anomalies found).
(b) Question-type frequency (taskType × count × % of points)
Counts cover all 6 years (245 parts); points cover 2021–2025 only (230 points; 2026 points unpublished).
| taskType | parts (6 yr) | points (2021–25) | % of points |
|---|---|---|---|
| calculation | 85 | 86 | 37.4% |
| justification (claim/choice + justify) | 32 | 25 | 10.9% |
| explanation (explain a phenomenon) | 28 | 25 | 10.9% |
| data-analysis (read/interpret/sketch graphs, tables, spectra) | 23 | 21 | 9.1% |
| prediction-with-reasoning (greater/less/equal + justify) | 22 | 21 | 9.1% |
| identification (state value/name/config) | 18 | 14 | 6.1% |
| write-equation (chemical eqns + K/Ksp/Ka/rate expressions) | 17 | 15 | 6.5% |
| particulate-representation (draw/critique particle diagrams) | 8 | 9 | 3.9% |
| experimental-design (procedures, steps, fault-finding) | 6 | 9 | 3.9% |
| draw-structure (Lewis diagrams, structural annotations) | 6 | 5 | 2.2% |
Headline: ~37% of FRQ credit is showing-your-work calculation; ~31% is verbal reasoning (justify/explain/predict); ~13% is representations (graphs, particles, structures); the rest is expressions/equations and short identifications. Every "greater/less/equal" or "agree/disagree" point requires the justification, not just the answer.
(c) Topic coverage — points per CED unit per year
Full points credited to the primary (first-listed) unit of each part; secondary-unit overlaps noted below. 2026 shown as part counts (points TBD).
| CED unit | 2021 | 2022 | 2023 | 2024 | 2025 | 5-yr pts | % of 230 | 2026 parts |
|---|---|---|---|---|---|---|---|---|
| 1 Atomic structure | 4 | 3 | 7 | 3 | 5 | 22 | 9.6% | 2 |
| 2 Compound structure/bonding | 2 | 2 | 6 | 3 | 3 | 16 | 7.0% | 6 |
| 3 Properties/IMFs/gases/solutions/spectroscopy | 14 | 10 | 5 | 6 | 9 | 44 | 19.1% | 6 |
| 4 Reactions/stoichiometry | 7 | 6 | 4 | 4 | 1 | 22 | 9.6% | 2 |
| 5 Kinetics | 1 | 4 | 4 | 4 | 4 | 17 | 7.4% | 3 |
| 6 Thermochemistry | 4 | 3 | 6 | 7 | 6 | 26 | 11.3% | 7 |
| 7 Equilibrium | 3 | 7 | 6 | 4 | 6 | 26 | 11.3% | 6 |
| 8 Acids–bases | 4 | 5 | 4 | 8 | 6 | 27 | 11.7% | 8 |
| 9 Thermo/electrochem | 7 | 6 | 4 | 7 | 6 | 30 | 13.0% | 3 |
Secondary-unit mentions (parts dual-mapped): U4 ×9, U1 ×6, U8 ×6, U3 ×5, U2/U6/U7 ×2 each, U5 ×1 — Unit 4 stoichiometry is the most common embedded skill inside other units' questions.
Course-build implications: Unit 3 is the largest single FRQ pool (gas law, IMF explanations, solution prep/dilution, Beer-Lambert all live there); Units 6–9 together are ~47% of FRQ points; kinetics is reliably exactly ~4 pts/yr (one dedicated short question or a long-question segment); every unit appears every year at ≥1 point except none — coverage is genuinely comprehensive annually.
(d) Recurring archetypes
Instance notation: year Q(parts). Bold = appears in 4+ of the 6 years.
A1. Calorimetry chain — q = mcΔT → molar ΔH (sign!) → perturbation or heat-loss error prediction. Every year. Parts/skills: read/choose ΔT, mass of solution vs reactant, q→mol rxn→ΔH, "greater/less/equal" on changed mass or imperfect insulation. Instances (7): 2021 Q4(a–c); 2022 Q1(c); 2023 Q3(f–g.ii); 2024 Q1(e.i–e.iii); 2024 Q4(a–d); 2025 Q3(c.i–d); 2026 Q1(b–e).
A2. Titration curve + Ka determination — pKa at half-equivalence, molarity from equivalence volume, sketch curve / place X, H-H ratio, indicator choice. Instances (4): 2022 Q1(e–h); 2024 Q1(c–d.iii); 2025 Q2(b.i–b.iii); 2026 Q3(d–f, h).
A3. Weak acid/base K math — Ka/Kb expression, ICE pH, Ka·Kb = Kw, pKa↔Ka, particulate weak-vs-strong recognition. Instances (5): 2021 Q1(a–b); 2023 Q5(c); 2024 Q2(f); 2025 Q7(b.i–b.ii); 2026 Q3(a–c).
A4. Buffer identification + justification — equimolar buffer pH = pKa (dilution-invariant), H-H ratio at given pH, buffer prep. Instances (3): 2023 Q4(a–c); 2024 Q2(g); 2025 Q2(b.iii).
A5. Solubility equilibria (Ksp suite) — Ksp expression/value, molar solubility, Q vs Ksp precipitation, common-ion, acid-enhanced solubility, conductivity/particulate evidence. 5 of 6 years. Instances (5): 2021 Q6(a–d); 2022 Q7(b.i–b.iii); 2023 Q7(a–c); 2025 Q1(e.i–f); 2026 Q1(f.i–f.iii).
A6. Thermodynamic favorability chain — ΔS° sign (particle reasoning) and/or ΔS° calc → ΔG° = ΔH° − TΔS° → temperature window / enthalpy- vs entropy-driven claim. 5 of 6 years. Instances (5): 2021 Q2(d–f); 2022 Q2(c.i–c.ii); 2024 Q2(d–e); 2025 Q3(b.i–b.ii); 2026 Q4(c).
A7. Galvanic cell chain — half-reaction/net ionic from reduction-potential table, E°cell, sign of ΔG° (−nFE°), ΔG at equilibrium, electrode-mass stoichiometry. Instances (4): 2022 Q3(e–g); 2023 Q1(f.i–f.iv); 2025 Q6(a–d); 2026 Q2(c).
A8. Electrolysis + Faraday's law — minimum voltage/external power, g or s from I·t via mol e⁻. Instances (3): 2021 Q5(a–c); 2024 Q3(d.i–e); 2026 Q2(d).
A9. Rate law / rate constant determination — order from initial-rates table or linearized plots, k with units, relative rates from stoichiometry. 5 of 6 years. Instances (5): 2022 Q5(a); 2023 Q3(d); 2024 Q6(a–b); 2025 Q2(c.i–c.ii); 2026 Q2(e–g).
A10. Mechanism & catalyst analysis — rate-determining step matching the rate law; catalyst consumed-then-regenerated; k independent of concentration. Instances (3): 2021 Q1(g); 2022 Q5(b–c); 2025 Q7(c).
A11. Collision-model rate reasoning — surface area / concentration effects on time-to-completion via collision frequency. Instances (2): 2023 Q3(b–c); 2024 Q2(b.i–b.ii).
A12. Gas-phase equilibrium package — K expression, K from particle diagram or partial pressures (mole fraction × Ptotal), Q vs K after volume change, K(T) from ΔH°. 5 of 6 years. Instances (5): 2022 Q2(d–g); 2023 Q2(e–f); 2024 Q5(a–b.iii); 2025 Q3(f.i–f.ii); 2026 Q4(b) (+2026 Q3(c.ii) K(T) in acid context).
A13. Lewis / VSEPR / formal charge / hybridization suite — complete or choose Lewis diagrams, resonance/formal charge, geometry, bond angles, hybridization. Every year. Instances (11): 2021 Q1(c); 2022 Q2(b), Q7(a); 2023 Q2(d.i–d.ii); 2024 Q6(c.i–c.ii); 2025 Q3(a), Q4(a), Q5(a); 2026 Q2(a.i–a.ii), Q5(a–b).
A14. IMF comparative property explanation — rank/explain bp, mp, ΔHvap, vapor pressure, solubility via LDF/dipole/H-bond/ion-dipole (polarizability arguments). Every year except 2024. Instances (8): 2021 Q2(b); 2022 Q1(d), Q4(b); 2023 Q6(a–c); 2025 Q2(d), Q4(b), Q5(b–c); 2026 Q5(c.i–c.ii).
A15. Atomic structure & Coulombic periodicity — electron configuration; explain radius/IE/lattice-enthalpy/ion-hydration trends via shells + Coulomb's law. Every year. Instances (8): 2021 Q2(a.ii, h); 2022 Q3(a–b); 2023 Q1(a.i–a.ii); 2024 Q3(b.ii); 2025 Q1(b.i–b.ii); 2026 Q1(a.i–a.ii), Q7(c).
A16. Spectra interpretation (mass spec / PES) — read or complete mass spectrum; draw/interpret PES peaks. Instances (3): 2021 Q2(a.i), Q2(g); 2025 Q1(a.i–a.ii).
A17. Solution preparation / dilution procedure — M1V1 = M2V2 calc plus fill-in-the-steps volumetric-flask or buret procedure. Instances (4): 2021 Q3(d–e); 2022 Q3(c), Q6(b.i–b.ii); 2023 Q4(b); 2024 Q7(a–b).
A18. Beer-Lambert calibration + error analysis — optimal wavelength, concentration from calibration curve, dilution back-calculation, contaminated-cuvette / overfilled-flask fault analysis. Instances (3): 2021 Q3(f–g); 2022 Q6(a–c); 2026 Q6(a–c).
A19. Ideal gas law + KMT / real gas — PV = nRT (n, P, V, density), partial pressure, KMT explanation of T/V behavior, deviation near condensation. Instances (5): 2021 Q1(f), Q7(a–d); 2023 Q5(a.i–a.ii); 2024 Q2(a.ii); 2025 Q5(d).
A20. Core stoichiometry — gravimetric analysis, limiting reactant from data, % yield reasoning, empirical formula from combustion/wet chemistry, excess-reactant concentration. Every year. Instances (8): 2021 Q3(a–c); 2022 Q1(a–b); 2023 Q1(b–e), Q3(e); 2024 Q2(a.i, c), Q3(c); 2025 Q2(a.i–a.ii); 2026 Q7(b).
A21. Hess's law / formation enthalpy — combine reactions with algebra; ΔHf bookkeeping. Instances (3): 2023 Q2(b); 2025 Q3(e); 2026 Q7(a).
A22. Redox identification via oxidation numbers — is it redox / what is oxidized/reduced. Instances (4): 2021 Q1(e); 2022 Q2(a); 2024 Q3(a); 2026 Q2(b.ii).
A23. Particulate diagram construction/critique — draw products with mass/charge/phase conservation; hydration shells; count particles to match Q/absorbance; find the error in a drawing. Nearly every year. Instances (8): 2021 Q6(c); 2022 Q3(d); 2023 Q5(b), Q7(a); 2024 Q1(d.i), Q4(b), Q5(b.i); 2026 Q6(a).
A24. Experimental error / procedure critique — "if X went wrong, is the measured value high/low/unchanged? justify" and "which step was executed incorrectly?" Every year; usually the last point of a lab-based question. Instances (9): 2021 Q3(g); 2022 Q1(b), Q6(c); 2023 Q1(e); 2024 Q1(e.iii); 2025 Q3(d); 2026 Q1(d), Q6(c) (+2021 Q4(c) as perturbation variant).
(e) Integration questions (archetypes spanning multiple units)
Cross-unit by construction: - A1 Calorimetry chain: U6 + U4 (q→mol rxn needs stoichiometry) + error analysis. The single most reliable integration point. - A2 Titration: U8 + U4 (4.6 titration stoichiometry); 2026 Q3 adds U7 (K2 from Ka/Kw). - A5 Ksp suite: U7 + U8 when acid attacks the anion (2022 Q7b.iii, 2025 Q1f); + U3 particulate/conductivity evidence (2021 Q6). - A6 Favorability chain: U9 + U6 (ΔH from calorimetry or Hess feeds ΔG); 2021 Q2 adds U5 (kinetic control: favorable but needs high T). - A7/A8 Electrochemistry: U9 + U4 (electrode-mass and Faraday stoichiometry, redox ox-numbers). - A12 Equilibrium package: U7 + U3 (mole fraction/partial pressure) + U6 (K(T) from ΔH°: 2025 Q3f.ii, 2026 Q3c.ii). - A15 Coulombic reasoning: U1 logic exported into U3 (ion-dipole hydration, 2025 Q1b) and U2 (lattice enthalpy, 2026 Q7c; alloys, 2024 Q3b).
Long questions (Q1–Q3) are themselves designed as integrations — each anchors a substance/lab and walks 3–5 units: - 2021 Q1 formic acid: U8→U2→U4→U3→U5. 2021 Q2 silicon: U1→U3→U4→U9→U5. - 2022 Q1 salicylic acid: U4→U6→U3→U8. 2022 Q3 Al/Ag⁺: U1→U3→U4→U9. - 2023 Q1 manganese: U1→U9. 2023 Q3 CaCO3/HCl: U4→U5→U6. - 2024 Q1 lactic acid: U8→U6 (+U3). 2024 Q3 sterling silver: U4→U2→U1→U9. - 2025 Q1 magnesium: U1→U3→U8→U7. 2025 Q3 white phosphorus: U2→U9→U6→U7. - 2026 Q1 KCl: U1→U6→U7. 2026 Q2 chromate: U2→U4→U9→U5. 2026 Q3 HNO2: U8→U7. Short questions are usually single- or two-unit (the pure-kinetics short Q appears in 2022, 2024; pure-gas 2021 Q7; pure-IMF 2023 Q6, 2025 Q5, 2026 Q5; pure-thermo 2021 Q4, 2024 Q4, 2026 Q7).
Verification & caveats
- Point sums verified programmatically: every long question = 10, every short = 4, every year (2021–2025) = 46. No SG point-sum discrepancies found.
- 2026: no SG; per-part points null; structure implies 46 total (10/10/10/4/4/4/4). 2026 Q2/Q3/Q6 are "Version J" of a multi-version digital administration.
- 2022: FRQ booklet PDF absent; content descriptions cross-checked against the Chief Reader report (task, topics, and per-part learning objectives), not the SG alone.
- 2024:
ap24-apc-chemistry-q1.pdf(sample responses) failed text extraction per MANIFEST — not needed for the registry (booklet + SG intact).