Chemistry: Mole Logic, Trends and Functional Groups
Chemistry contributes 35 questions and rewards a mix of recall, reasoning, and numerical accuracy. The syllabus is Class 11-12: atomic structure, chemical bonding, thermodynamics, equilibrium, redox and electrochemistry, kinetics, solutions, coordination compounds, p-block and d-block elements, and organic chemistry including biomolecules.
Physical chemistry
Mole concept, gas laws, thermochemistry, Le Chatelier's principle, pH and buffers, solubility product, electrochemical cells, and rate laws. Numerical questions often hinge on a single balanced equation.
Inorganic chemistry
Periodic trends, hybridisation and molecular geometry, coordination number and isomerism, and characteristic reactions of s- and p-block elements. Learn exceptions rather than isolated facts.
Organic chemistry
Functional-group reactions, isomerism, inductive and resonance effects, and named reactions. Predict products by identifying the electrophile or nucleophile and the stability of intermediates.
Worked example
How many moles of KMnO4 oxidise 1 mole of FeSO4 in acidic medium? In acid, MnO4- gains 5 electrons (Mn from +7 to +2), while Fe2+ loses 1 electron. One mole of KMnO4 therefore accepts 5 moles of electrons and oxidises 5 moles of Fe2+. For 1 mole of Fe2+, moles of KMnO4 = 1/5 = 0.2.
Traps
- Forgetting that KMnO4 behaviour changes with medium (acidic, neutral, alkaline).
- Not balancing redox half-reactions before using mole ratios.
- Confusing empirical and molecular formulas.
- In organic items, ignoring stereochemistry or the major-product rule.