Chemistry
Chemistry tests atomic structure, periodic trends, chemical bonding, the mole concept, solutions, equilibrium, electrochemistry, corrosion, and basic nuclear and water chemistry relevant to a power plant. The exam favours calculation-based stoichiometry and concept comparisons over long descriptive answers.
Core rules
- Aufbau, Pauli exclusion, and Hund's rules determine electron configuration.
- Across a period, atomic radius decreases and electronegativity increases; down a group, radius increases and ionisation energy generally decreases.
- Ionic bonds form by electron transfer, covalent bonds by sharing; polar covalent bonds show unequal sharing.
- Mole concept: n = m/M; molarity = moles of solute per litre of solution.
- pH = −log[H⁺] for dilute aqueous solutions at 25 °C.
- Corrosion control uses sacrificial anodes, protective coatings, and dissolved-oxygen control.
Worked example. 20 mL of 0.1 M HCl is diluted to 200 mL. Moles of HCl = 0.020 × 0.1 = 0.002 mol. New concentration = 0.002 / 0.200 = 0.01 M. Since HCl is a strong monobasic acid, [H⁺] = 0.01 M and pH = −log(0.01) = 2. Dilution by a factor of 10 raises pH by one unit.
Traps. Do not treat weak acids as fully dissociated; keep volume in litres for molarity; normality and molarity differ for polyprotic acids; pH is temperature-dependent; balance nuclear equations by mass number and atomic number, not by charge alone.