Chemistry
The Chemistry domain of MP PAT checks atomic structure, periodic trends, chemical bonding, mole calculations, acids–bases, equilibrium, and basic organic chemistry. Questions reward precise definitions and unit-aware calculation.
Atomic structure and periodic trends
- Electrons fill shells/orbitals in order; valence electrons control group behavior.
- Across a period, atomic radius decreases and electronegativity increases; down a group, radius increases and ionization energy generally decreases.
- Metals lose electrons; nonmetals gain or share.
Bonding, moles, and equilibrium
- Ionic bonds transfer electrons; covalent bonds share them.
- Mole: n = mass ÷ molar mass; one mole contains 6.022 × 10²³ particles.
- pH = −log[H⁺]; strong acids dissociate fully, weak acids partially.
- Le Chatelier’s principle predicts shifts in concentration, pressure, or temperature.
Organic basics
- Identify functional groups (alcohol -OH, aldehyde -CHO, carboxylic acid -COOH) and apply IUPAC naming.
Worked example
How many molecules and atoms are in 11 g of CO2? Molar mass = 12 + 2(16) = 44 g/mol. n = 11 ÷ 44 = 0.25 mol. Molecules = 0.25 × 6.022 × 10²³ = 1.5055 × 10²³. Each CO2 has 3 atoms, so atoms = 3 × 1.5055 × 10²³ = 4.5165 × 10²³.
Traps that cost marks
- Using 44 g/mol for a different gas or forgetting Avogadro’s number.
- Treating pH as a linear scale; ignoring weak-acid dissociation.
- Confusing empirical and molecular formulae; missing functional-group priority in naming.