AP Chemistry Formula Sheet 2026 — Complete Equation & Reference Guide
The AP Chemistry exam provides a multi-page reference sheet including equations, constants, the periodic table, and an electrochemical series. Here is the complete reference with context for every section.
AP Chemistry Reference Sheet: What's Provided
The AP Chem reference sheet is one of the most comprehensive among all AP exams. It includes atomic structure, equilibrium, thermodynamics, electrochemistry, kinetics, and solution chemistry.
Atomic Structure and Periodicity
$$E = h\nu \qquad \lambda\nu = c$$
$$E_n = -\frac{2.178 \times 10^{-18}}{n^2} \text{ J}$$
$$\lambda = \frac{h}{mv}$$ (de Broglie wavelength)
| Constant | Value |
|---|---|
| Speed of light (c) | 3.00 × 10⁸ m/s |
| Planck's constant (h) | 6.626 × 10⁻³⁴ J·s |
| Avogadro's number (N_A) | 6.022 × 10²³ mol⁻¹ |
| Electron charge (e) | 1.602 × 10⁻¹⁹ C |
| 1 eV | 1.602 × 10⁻¹⁹ J |
| Faraday's constant (F) | 96,485 C/mol |
| Gas constant (R) | 8.314 J/(mol·K) or 0.08206 L·atm/(mol·K) |
Equilibrium
Equilibrium expression: $$K_c = \frac{[\text{products}]^{\text{coefficients}}}{[\text{reactants}]^{\text{coefficients}}}$$
Relationship between K_p and K_c: $$K_p = K_c(RT)^{\Delta n}$$
where Δn = moles of gaseous products − moles of gaseous reactants
Reaction quotient: $$Q = \frac{[\text{products}]}{[\text{reactants}]}$$
- Q < K: reaction proceeds forward
- Q > K: reaction proceeds reverse
- Q = K: at equilibrium
Acid dissociation: $$K_a = \frac{[\text{H}^+][\text{A}^-]}{[\text{HA}]}$$
Base dissociation: $$K_b = \frac{[\text{OH}^-][\text{BH}^+]}{[\text{B}]}$$
Water dissociation: $$K_w = [\text{H}^+][\text{OH}^-] = 1.0 \times 10^{-14} \text{ at } 25°\text{C}$$
$$K_a \times K_b = K_w$$
pH: $$\text{pH} = -\log[\text{H}^+] \qquad \text{pOH} = -\log[\text{OH}^-]$$
$$\text{pH} + \text{pOH} = 14 \text{ at } 25°\text{C}$$
Henderson-Hasselbalch equation: $$\text{pH} = pK_a + \log\frac{[\text{A}^-]}{[\text{HA}]}$$
Solubility product: $$K_{sp} = [\text{cation}]^m[\text{anion}]^n$$
Thermodynamics
Standard enthalpy of reaction (Hess's Law): $$\Delta H°_{rxn} = \sum \Delta H°_f(\text{products}) - \sum \Delta H°_f(\text{reactants})$$
Entropy: $$\Delta S°_{rxn} = \sum S°(\text{products}) - \sum S°(\text{reactants})$$
Gibbs free energy: $$\Delta G° = \Delta H° - T\Delta S°$$
$$\Delta G° = -RT\ln K$$
$$\Delta G = \Delta G° + RT\ln Q$$
Spontaneity from ΔG:
| ΔH | ΔS | Spontaneous? |
|---|---|---|
| − | + | Always (ΔG always −) |
| + | − | Never (ΔG always +) |
| − | − | Only at low T |
| + | + | Only at high T |
Calorimetry: $$q = mc\Delta T \qquad q = C\Delta T$$
$$q_{rxn} = -q_{solution}$$
Electrochemistry
Standard cell potential: $$E°{cell} = E°{cathode} - E°_{anode}$$
$$\Delta G° = -nFE°_{cell}$$
$$E°_{cell} = \frac{RT}{nF}\ln K = \frac{0.0257}{n}\ln K \text{ at 25°C}$$
Nernst equation: $$E = E° - \frac{0.0592}{n}\log Q \text{ at 25°C}$$
Electrolysis — Faraday's law: $$\text{moles of substance} = \frac{It}{nF}$$
where I = current (A), t = time (s), n = electrons transferred
Kinetics
Rate law: $$\text{rate} = k[\text{A}]^m[\text{B}]^n$$
Integrated rate laws:
| Order | Rate Law | Integrated | Half-life |
|---|---|---|---|
| 0 | rate = k | [A] = [A]₀ − kt | t½ = [A]₀/2k |
| 1 | rate = k[A] | ln[A] = ln[A]₀ − kt | t½ = 0.693/k |
| 2 | rate = k[A]² | 1/[A] = 1/[A]₀ + kt | t½ = 1/(k[A]₀) |
Arrhenius equation: $$k = Ae^{-E_a/RT}$$
$$\ln\frac{k_2}{k_1} = \frac{E_a}{R}\left(\frac{1}{T_1} - \frac{1}{T_2}\right)$$
Gases
Ideal gas law: $$PV = nRT$$
Combined gas law: $$\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$$
Dalton's law of partial pressures: $$P_{total} = \sum P_i \qquad P_i = \chi_i P_{total}$$
Graham's law of effusion: $$\frac{r_1}{r_2} = \sqrt{\frac{M_2}{M_1}}$$
van der Waals (non-ideal): $$\left(P + \frac{an^2}{V^2}\right)(V - nb) = nRT$$
Solutions and Colligative Properties
Molarity: $$M = \frac{\text{mol solute}}{\text{L solution}}$$
Molality: $$m = \frac{\text{mol solute}}{\text{kg solvent}}$$
Boiling point elevation: $$\Delta T_b = K_b \cdot m \cdot i$$
Freezing point depression: $$\Delta T_f = K_f \cdot m \cdot i$$
Osmotic pressure: $$\pi = MRT$$
What's NOT on the Formula Sheet (Must Memorize)
| Concept | What to Know |
|---|---|
| Net ionic equations | Must write from scratch — cancel spectator ions |
| Solubility rules | Which ionic compounds are soluble/insoluble |
| Oxidation state rules | O is -2, H is +1, group 1 is +1, etc. |
| Common polyatomic ions | Sulfate, nitrate, phosphate, carbonate, etc. |
| Strong acids and bases | HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄; LiOH, NaOH, KOH, Ca(OH)₂, etc. |
| ICE table method | For equilibrium, weak acid/base, buffers |
| Formal charge formula | FC = valence e⁻ − nonbonding e⁻ − ½ bonding e⁻ |
| Hybridization | sp, sp², sp³, sp³d, sp³d² from geometry |
| Balancing redox in acidic/basic | Half-reaction method |
AP Chem Formula Sheet Exam Tips
- No calculator on MC — the 60 MC questions require you to estimate and do mental math. Memorize common logs: log 2 ≈ 0.30, log 3 ≈ 0.48, log 5 ≈ 0.70
- ICE tables appear every year on FRQ — practice setting them up quickly
- Henderson-Hasselbalch is the #1 most useful formula for buffer FRQ questions
- Nernst equation always uses log base 10 (not ln) in the 0.0592/n form
- ΔG° = -nFE° and ΔG° = -RT ln K connect electrochemistry to thermodynamics — a common FRQ link
Common AP Chemistry Exam Tasks
- Stoichiometry calculations — mole conversions, limiting reagent, percent yield. These appear on both the no-calculator MC and FRQ sections. Mental math and estimation skills matter.
- Equilibrium problems — write the equilibrium expression, set up an ICE table, solve for concentrations. Know Le Chatelier's principle and how to predict shifts.
- Electrochemistry — calculate cell potential ($E°_{cell} = E°_{cathode} - E°_{anode}$), determine spontaneity from $\Delta G = -nFE$, and write half-reactions.
- Acid-base calculations — pH, pOH, Ka/Kb expressions, buffer problems using Henderson-Hasselbalch. Know strong vs. weak acid/base behavior.
- Thermodynamics — calculate $\Delta G = \Delta H - T\Delta S$, determine spontaneity at different temperatures, relate $\Delta G°$ to $K$.
Frequently Asked Questions
Does AP Chemistry provide a formula sheet?
Yes. AP Chemistry provides an official equation and data sheet on exam day that includes key formulas, constants, and the periodic table. However, knowing how and when to apply each equation still requires preparation — the sheet doesn't explain context or setup.
Why is AP Chemistry so hard?
AP Chemistry has a ~55% pass rate because it demands both conceptual understanding and mathematical precision simultaneously. The no-calculator MC section requires mental stoichiometry and estimation. The FRQ section expects written explanations, not just calculations.