Chemistry — Exam Writing Tips
How to write Chemistry answers for full marks in TGBIE — tips for reactions, structures, numericals, and inorganic questions.
Chemical Equations and Reactions
- 1Always balance equations. Write state symbols (s), (l), (g), (aq) wherever relevant — they earn marks.
- 2For 'Give the preparation' questions: write the balanced equation with reaction conditions (temperature, pressure, catalyst) above the arrow.
- 3For reaction mechanisms (SN1, SN2, electrophilic addition): show the intermediate with partial charges and curved arrows indicating electron movement.
- 4Don't skip writing the reagents and conditions — 'UV light', 'anhydrous AlCl₃', 'conc. H₂SO₄' are mark-carrying details.
Structure Drawing
- 1Draw structures clearly — Lewis structures for ionic/covalent bonding, orbital overlap diagrams for hybridisation.
- 2For VSEPR: draw the 3D shape (wedge-dash notation if needed), show lone pairs as dots, and label bond angles.
- 3For organic structures: use correct bond angles for sp (180°), sp² (120°), sp³ (109.5°). Don't draw flat benzene without the circle/resonance.
- 4For molecular orbital diagrams: label σ, σ*, π, π* orbitals in correct energy order; fill electrons from lowest energy up.
Thermodynamics and Equilibrium — Numerical Answers
- 1Always include units in every step: kJ/mol for ΔH, J/mol·K for ΔS, kJ/mol for ΔG.
- 2For Hess's law problems: number the given reactions, show which to reverse or multiply, then add step by step.
- 3For equilibrium calculations: set up ICE table (Initial, Change, Equilibrium) clearly before writing Kc expression.
- 4For pH calculations: show [H⁺] computation before taking the log. Write: pH = −log(x.xxx × 10⁻ⁿ) = n − log(x.xxx).
Inorganic Chemistry — Periodic Table Questions
- 1For 'explain the trend' questions: state the trend, give the reason (effective nuclear charge, shielding, atomic radius), then give an example.
- 2For anomalous property questions: state the anomaly first, then explain (e.g., 'Li is anomalous in Group 1 due to its small ionic size and high charge density').
- 3For diagonal relationship: list 3–4 common properties between the element and its diagonal neighbour.
- 4For preparation of compounds: write the chemical equation, then mention one important use or property.