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OSAT Chemistry study materials
OSAT Chemistry study resources

OSAT Chemistry: Chemistry Content Domain

OSAT Chemistry · Work through your exam, one topic at a time.

All guide sections

Chemistry Content Domain

Scope of the domain

The OSAT Chemistry content domain samples the full breadth of a secondary chemistry curriculum: atomic structure and periodicity, chemical bonding and intermolecular forces, stoichiometry, gas laws, solutions, kinetics, equilibrium, acid–base chemistry, thermodynamics, electrochemistry, organic/biochemistry basics, and laboratory safety. Expect items that ask you to predict, calculate, and explain-not merely recall definitions. Because the exam does not publish a finer subdomain list, build a connected model rather than memorizing isolated facts.

Core rules and concepts

  • Use the periodic table as a predictive tool: effective nuclear charge increases across a period, atomic radius decreases, ionization energy and electronegativity increase; down a group, radius increases and ionization energy decreases.
  • Balance equations and convert with moles; limiting reagent determines theoretical yield; percent yield = actual/theoretical ×100.
  • For gases, PV=nRT; at constant T and P, volumes react in mole ratios. For solutions, M=n/V and dilution M1V1=M2V2.
  • Equilibrium: Q vs K predicts direction; Le Châtelier shifts; weak acid/base calculations use Ka/Kb and ICE tables.
  • Thermo: ΔG=ΔH−TΔS; spontaneous at constant T,P when ΔG<0. Electrochem: E°cell = E°cathode − E°anode; positive E°cell means spontaneous.
  • Bonding: ionic compounds form between metals and nonmetals and have high melting points; molecular compounds share electrons; polarity depends on electronegativity differences and geometry. Intermolecular forces-hydrogen bonding > dipole–dipole > London dispersion-explain boiling points and solubility. Organic: functional groups determine reactivity; alkanes are saturated, alkenes/alkynes unsaturated. Lab: know significant figures and units.

Worked example

Example: 10.0 g CaCO3 (molar mass 100.09 g/mol) reacts with excess HCl. What volume of CO2 at STP forms? n(CaCO3)=10.0/100.09=0.0999 mol. CaCO3+2HCl→CaCl2+CO2+H2O gives 1:1 CO2, so n(CO2)=0.0999 mol. At STP, V=n×22.4 L/mol=2.24 L.

Traps that cost marks

Traps: forgetting to convert grams to moles; using limiting reagent as product amount; mixing K and Q; ignoring Δn in Kp=Kc(RT)^Δn; assigning oxidation numbers incorrectly; and overlooking safety-add acid to water, never water to acid.