Chemistry
TS ECET Chemistry tests atomic structure, chemical bonding, thermodynamics, equilibrium, solutions, electrochemistry, chemical kinetics, metallurgy, polymers, water treatment and organic functional groups. It mixes factual recall with short numerical work such as pH, normality and Faraday calculations.
Core rules
- Atomic structure: quantum numbers, Aufbau principle, Pauli exclusion and Hund's rule determine electron configuration.
- Bonding: VSEPR predicts shape; hybridisation explains geometry; bond order from molecular orbital theory indicates stability.
- Thermodynamics: ΔG = ΔH - TΔS; negative ΔG means spontaneous. Hess's law allows indirect enthalpy calculation.
- Equilibrium: Le Chatelier's principle predicts shift; pH = -log[H+]; buffers resist pH change.
- Solutions: molarity = moles/litre; normality = molarity × n-factor; dilution obeys M1V1 = M2V2.
- Electrochemistry: Nernst equation for cell emf; Faraday's laws relate charge to mass deposited.
- Kinetics: first-order half-life t1/2 = 0.693/k; Arrhenius equation links rate and temperature.
- Organic chemistry: identify functional groups by tests and IUPAC naming; isomerism changes properties.
Worked example
Calculate the pH of 0.01 M HCl. HCl is a strong monobasic acid, so [H+] = 0.01 = 10^-2 M. pH = -log(10^-2) = 2. The solution is acidic, as expected.
Traps
- Using molarity instead of normality in acid-base titration.
- Assuming a weak acid dissociates completely.
- Forgetting that dilution changes pH by only one unit for each tenfold change.
- Confusing ΔH and ΔG in spontaneity questions.
- Mixing up reagents in organic functional-group tests.