goh_wz

• Volume when resultant mixture of gases cooled to rt: Do not count H₂O

• Acidity of halo-substituted organic acids:
  unsubst < monosubst < disubst < trisubst;
  iodo < bromo < chloro < fluoro;
  closer to –COOH group, more acidic
• Distinguishing test: If reaction with one cpd, verify NAR with other cpd: look carefully at all functional groups!

1. Account for the trends in atomic radius, first ionisation energy and melting point across the period Na–Ar. 5 marks.
2. 3/4 page of information on six organic compounds. Using all the information, identify all of them and give equations to all reactions. 20 marks, no part-questions.
3. Draw dot-and-cross diagrams to illustrate the bonding in NaCl, PCl₃ and CO₂. Explain the bonding in PCl₃ and CO₂ in terms of orbital overlap [emphasis in original]. Illustrate with diagrams. 7 marks.
4. PLOT a graph of rate against [NH₃].

1. Account for the trends in atomic radius, first ionisation energy and melting point across the period Na–Ar. 5 marks.

• STATE SYMBOLS !!! × 2

• Taking data from tables: Be mindful of what the data actually is (no. of moles, concentration); manipulate if necessary

• Final answer conc too _low: Check conversion of units: cm³ → dm³
• Relative isotopic mass: Mass of 1 atom of the isotope

• Redox half-equations: Use Data Booklet
• Zinc is a strong reducing agent has a greater reduction potential compared to gold
• Fe²⁺/MnO₄⁻ titration: KMnO₄ will usually be ~1/5th as concentrated as FeSO₄ for comparable volumes titrated

• Inter-electron repulsion arising from 2 electrons occupying the same np orbital
• Large jump from (n − 1)^th to n^th ionisation energy, n^th electron particularly difficult to remove, n − 1 electrons in valence shell, Group n − 1
• Ionisation energy: always mention nuclear charge, effective nuclear charge

• Bond angle for tetrahedral electron-pair geometry with one lone pair (107°) and two lone pairs (105°)
• Bond angle for trigonal planar electron-pair geometry with one lone pair (SO₂: 119°)
• BF₃ is covalent while AlF₃ is ionic
• Diatomic molecules can be polar too, like ClF and HBr
• Wikipedia: "BN has a layered structure similar to graphite. Within each layer, boron and nitrogen atoms are bound by strong covalent bonds, whereas the layers are held together by weak van der Waals forces. The interlayer "registry" of these sheets differs, however, from the pattern seen for graphite, because the atoms are eclipsed, with boron atoms lying over and above nitrogen atoms. This registry reflects the polarity of the B–N bonds."
• NH₃, H₂O: Draw lone pair(s) at top
• Hydrogen bonding of NH₃, H₂O: 2nd molecule 90° rotated
• AlCl₃ 1 pair of electrons short of stable octet has an empty p-orbital to accept lone pair from NH₃ to form dative bond
• Silicon poor conductor because no mobile charge carriers limited free electrons and holes

• Enthalpy change is in kJ mol⁻¹
• Standard enthalpy change of reaction = Standard enthalpy change of combustion of reactants − Standard enthalpy change of combustion of products
• Applying mcΔT: for reactions involving powder and solution, do not add mass of powder into m
• Applying mcΔT: c = 4.18 J g⁻¹ K⁻¹
• Standard enthalpy change of combustion: The heat energy evolved when...
• Heat evolved → enthalpy change of reaction: remember to put minus !!!

• K_c is about concentration, not no. of moles

• Prove weak acid: Calculate [H⁺] and show [H⁺] << [acid]
• pH transition range of methyl orange (yellow 4.4–3.2 red); phenolphthalein (colourless 8.2–10.0 pink)
• "pH transition range of X lies within rapid pH change over equivalence point"
• Buffers: ... Nearly all the added H⁺ ions are removed

• Boltzmann distribution: Legend, label E_a

• Acid rain: SO_2(g) + H₂O_(l) → H₂SO_3(aq)
  absorbed by moisture in air
• NO generated in engine due to high temperature and pressure
• NO reduced by CO

9 Organic chemistry

• Alkene = C=C bond but can contain other functional groups
• Ethane-1,2-diol not ethan-1-2-diol

• For structural formulae of organic compounds after reactions, show resulting carboxylate ion together with anion: C₆H₅CH₂COO⁻Na⁺
• Write conditions of reaction above and below arrow (MnO₄⁻/H⁺, Δ for oxidation)
• Describing reactions: If redox, in place of "X reacts to form Y" use "X is oxidised (reduced) to form Y"

• Esters: Hydrolyse if necessary to test with tri-iodomethane test
• AlCohols: Add PCl₅ (rt), white fumes evolved
• Halogenoalkanes: (1) ethanolic NaOH, heat with reflux (2) cool (3) acidify with HNO₃ (4) add AgNO_3(aq) (Obs) Cl⁻ white; Br⁻ pale cream; I⁻ pale yellow ppt

• Nitriles oxidised to amines
• =CHCH= oxidised by hot, acidified KMnO₄ to 2CO₂ + H₂O not HOOCCOOH
• Oxidising aldehyde to carboxylic acid with benzene ring attached: Use K₂Cr₂O₇ not KMnO₄ to prevent side chain oxidation

• Markovnikoff's rule: Rich get richer; poor get poorer
• Double addition/substitution etc requires excess reagent

• Stereoisomerism: Same molecular formula, same structural formula, different spatial arrangement of atoms
• "Carboxylate anion forms 2 equivalent resonance structures with the negative charge delocalised over two highly electronegative O atoms"
• CFCs cause a hole in destruction of the ozone layer

毎日　毎日　書いてるラブレター

The love letters that I'm writing every day, every day

いつか本にして出したなら　売れると思うんだ

If they were some day made into a book, I think it would sell

「想いを伝えたい人に贈りたい一冊！」なんて

"A book for people wishing to convey their yearning!"