Chapters

1 · Formulas and when each holds

• pH = −log[H⁺]; pH + pOH = 14 at 25 °C.
• Weak acid: [H⁺] = √(Ka·C), when the degree of dissociation is small.
• Buffer (Henderson): pH = pKa + log([salt]/[acid]).
• Salt of weak acid and strong base: pH = 7 + ½(pKa + log C).

2 · Question types and the first step

• Buffer questions: find the ratio of salt to acid before anything else.
• Solubility product: write s in terms of Ksp from the formula of the salt.

3 · Traps

Common ion: solubility falls in a solution that already holds one of the ions.

Buffer on dilution: he diluted the acid alone. Rule: dilution changes salt and acid equally, so the ratio and the pH stay.

4 · My additions

• Check the temperature before using 14.

1 · Formulas and when each holds

• Bond order (MOT) = ½(bonding − antibonding electrons).
• Hybridisation: count σ bonds and lone pairs on the central atom.
• Dipole moment is a vector: symmetric shapes cancel.

2 · Question types and the first step

• Shape questions: count electron pairs, then name the geometry, then the shape.
• Magnetic behaviour: write the MO filling and look for unpaired electrons.

3 · Traps

O₂ is paramagnetic: two unpaired electrons in π* orbitals.

4 · My additions

• s-p mixing changes the order for B₂, C₂, N₂.