Chemistry (Chemistry / Basic Chemistry)
What the exam tests
Chemistry and Basic Chemistry test stoichiometry, gas laws, equilibrium, acid-base chemistry, redox and electrochemistry, and organic functional groups. Both calculation and structural reasoning are required.
Core rules
- Mole: n=m/M; at STP, 22.4 L per mole of ideal gas, or use PV=nRT.
- Balance equations before using mole ratios; identify the limiting reagent.
- Equilibrium: the K expression excludes pure solids and liquids; Le Chatelier predicts direction, not rate.
- Acid-base: pH=-log[H+]; strong acids and bases fully dissociate; buffers resist pH change.
- Organic: functional groups determine reactions; isomers have the same formula but different structure.
Worked example
20.0 mL of 0.10 M HCl is neutralized by 0.20 M NaOH. Moles HCl = 0.0200 times 0.10 = 0.00200 mol. The reaction is 1:1, so NaOH moles = 0.00200 mol. Volume = 0.00200/0.20 = 0.0100 L = 10.0 mL. Reasoning: convert volume to moles, use the balanced ratio, then convert back to volume.
Traps
Forgetting to convert mL to L; using the wrong mole ratio; ignoring the limiting reagent; writing equilibrium constants with solids; confusing oxidation and reduction; and missing stereochemical or positional isomers. In organic answers, name the group and reaction type explicitly.