AP Chemistry case studies
AP Chemistry · Put your knowledge to work in context.
AP Chemistry is an advanced placement course and exam intended to mirror a one-year, introductory college general chemistry course. It suits students who have already taken high school chemistry and Algebra II and who want to build fluency in quantitative problem solving, experimental design, and molecular-level reasoning about matter. The AP Chemistry case studies are 5 cases and about 3,412 words.
1Reading a Photoelectron Spectrum: Group Number, Shielding, and an Ionization-Energy Anomaly
A sample of an unidentified main-group element is analyzed by photoelectron spectroscopy. The spectrum shows five peaks whose relative areas are 2 : 2 : 6 : 2 : 3, listed in order of decreasing binding energy, with measured binding energies of approximately 2150 eV, 190 eV, 135 eV, 19 eV, and 11 eV.
703 words, about 4 min2Three 16-Electron Linear Triatomics: Resonance, Formal Charge, and Measured Bond Lengths
Three linear triatomic species with 16 valence electrons are examined: CO₂, N₃⁻, and SCN⁻. Measured bond lengths are: both C–O bonds in CO₂ = 116 pm; both N–N bonds in N₃⁻ = 116 pm; in SCN⁻, S–C = 168 pm and C–N = 118 pm (typical single-bond values for comparison: S–C ≈ 181 pm, C–N ≈ 147 pm; C–N triple bond ≈ 116 pm).
685 words, about 3 min3Positive Deviation from Raoult's Law in a Two-Liquid Mixture
Two volatile, mutually miscible liquids, X (molar mass 58 g/mol) and Y (molar mass 74 g/mol), are studied at 25 °C. The vapor pressures of the pure liquids at this temperature are P°(X) = 120 torr and P°(Y) = 40 torr.
695 words, about 3 min4Rate Law, a Badly Chosen Mechanism, and the Activation Energy
The reaction 2 A(g) + B(g) → C(g) is studied at 300 K by measuring initial rates from the appearance of C. Trial 1: [A]₀ = 0.100 M, [B]₀ = 0.100 M, rate = 2.0 × 10⁻⁴ M s⁻¹ Trial 2: [A]₀ = 0.200 M, [B]₀ = 0.100 M, rate = 8.0 × 10⁻⁴ M s⁻¹ Trial 3: [A]₀ = 0.100 M, [B]₀ = 0.200 M, rate = 2.0 × 10⁻⁴ M s⁻¹ A proposed mechanism is: Step 1: A + A ⇌ A₂ (fast equilibrium) Step 2: A₂ + B → C (slow) A separate run at 320 K with [A]₀ = [B]₀ = 0.100 M gives an initial rate of 8.0 × 10⁻⁴ M s⁻¹.
675 words, about 3 min5Weak-Acid Titration: Equivalence-Point pH, Buffer Point, and Indicator Choice
A 25.0 mL sample of 0.100 M HA (Ka = 1.8 × 10⁻⁵ at 298 K) is titrated with 0.100 M NaOH. The measured initial pH is 2.87, and at 12.5 mL of added base the pH is 4.74.
654 words, about 3 min