Survey of the Natural Sciences - General Chemistry
What the general chemistry section tests
This section covers stoichiometry, gas laws, atomic structure and periodic trends, thermodynamics, kinetics, equilibrium, acids and bases, electrochemistry, and solution chemistry. The exam favors multi-step calculations and conceptual comparisons, so track units and limiting reagents.
Core rules
- Stoichiometry: balance the equation first; convert mass to moles; the limiting reagent determines theoretical yield.
- Gases: use Kelvin. PV=nRT; at constant T and n, P1V1=P2V2.
- Thermodynamics: ΔG=ΔH−TΔS; spontaneous means ΔG<0. Negative ΔH favors spontaneity; positive ΔS favors it.
- Equilibrium: Keq expressions exclude pure solids and liquids. Le Châtelier shifts oppose a stress.
- Acids/bases: strong acids dissociate completely; pH=−log[H+]. A weak acid needs Ka and an ICE table.
Worked example
4 mol H2 reacts with 1 mol O2: 2H2+O2→2H2O. Moles of H2 needed for 1 mol O2 = 2 mol, so H2 is in excess and O2 is limiting. O2 produces 2 mol H2O. If the question asks for mass, multiply by 18.02 g/mol to get about 36.0 g.
Traps
- Using Celsius in gas laws.
- Calling H2 limiting because 4 > 1 without comparing stoichiometric ratios.
- Including water in a Keq expression for an aqueous reaction; pure liquids are omitted.
- Confusing pH and pOH; pH+pOH=14 only at 25 °C.
- Reporting more significant figures than the data allow.