Chemistry
What the exam tests
Expect atomic structure (protons, neutrons, electrons, isotopes), the periodic table and its groups, chemical bonding (ionic, covalent, metallic), chemical formulas and equations, moles and molar mass, acids/bases/salts and pH, plus simple organic chemistry (hydrocarbons, functional groups).
Traps to expect
- Balancing: coefficients change, subscripts do not.
- Ionic vs covalent: metals + non-metals usually form ionic bonds.
- Mole calculations: molar mass is g/mol; n = m/M.
- pH scale: pH < 7 acidic, 7 neutral, > 7 basic; each unit is a tenfold change in H⁺ concentration.
- Isotopes: same protons, different neutrons, so different mass number.
Rule of thumb
Balance equations by counting each element on both sides; then check charge if ions are involved.
Worked example
How many moles in 36 g of water (H₂O, M = 18 g/mol)? n = m/M = 36/18 = 2 mol. That contains 2 × 6.02 × 10²³ = 1.204 × 10²⁴ molecules.