Chapters
Graded once a chapter has 10 timed answers: papers, part tests, chapter tests and timed past-paper sets (a 15-question strength check, Grade it, among them). Recent answers count more: one 90 days old counts half. His whole record counts as 5 questions more, so an old weakness fades but is never dropped. The line gives the score, his last 60 days and his last test.2 of 4 chapters have a note · jump to
Ionic Equilibrium
Chemistry · Weak 36% · Revised by the coach 14 Nov: Added the trap from the buffer doubt
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.
Chemical Bonding
Chemistry · Shaky 53% · Saved 3 Nov: First version, from the class module
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.
Coordination Compounds
Chemistry · Shaky 53%
No note yet.
Alkyl Halides
Chemistry · Weak 33%
No note yet.