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[info]goh_wz
partially friends only

#418 HAHA EVEN THE JAPAN PEOPLE HAVE CAUGHT ON
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[info]goh_wz
Jodie (・´ェ`・) says (11:51 PM):
i think you should work on your introduction
give it more BOOMZ
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Chemistry notes to self: MCQ
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1 Atoms, molecules and stoichiometry
  • Volume when resultant mixture of gases cooled to rt: Do not count H2O
9 Organic chemistry
  • 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!
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Highlights of H1 Chem P2
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Things that made me go x.x during H1 Chem
  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].
Now a blow-by-blow account:
  1. Account for the trends in atomic radius, first ionisation energy and melting point across the period Na–Ar. 5 marks.
5 marks for what must have taken 9,023,823 pages in my lecture notes??? Typically it's one property for 2–3 marks even in prelim exams, and because this is A Levels where you get 1 mark for writing down just the number of electrons in HCO3 (ans: 32), it should really be 3–4 marks per property. Because it was such a conditioned response for me to vomit out every single bit I memorised whenever such questions are asked, it imposed a lot more mental stress as I, for perhaps the first time (even though my 4x prelim papers were all timed) actually had to select what to write. Obviously Cambridge knows that they can't expect much out of 5 marks, so I'm crossing my fingers that what I, against my PRIMORDIAL INSTINCTS, jettisoned were exactly the things which were not needed (seriously, not writing things down when you know there's more to the answer caused me a lot of stress).

the rest! )

Chemistry notes to self
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Things to do at the end of the exam
  • CHECK ALL EQUATIONS FOR STATE SYMBOLS
  • CHECK ENTHALPY CHANGES FOR CORRECT SIGN (ESP. CALCULATED FROM HEAT EVOLVED)
Chemistry notes to self 2009
Distilled from Specimen paper, SAJC(H1)/2007/II, SRJC(H1)/2007/II, YJC(H1)/2007/II
  • STATE SYMBOLS !!! × 2
  • Taking data from tables: Be mindful of what the data actually is (no. of moles, concentration); manipulate if necessary
1 Atoms, molecules and stoichiometry
  • Final answer conc too low: Check conversion of units: cm3 → dm3
  • Relative isotopic mass: Mass of 1 atom of the isotope
2 Redox reactions
  • 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
3 Atomic structure
  • Inter-electron repulsion arising from 2 electrons occupying the same np orbital
  • Large jump from (n − 1)th to nth ionisation energy, nth electron particularly difficult to remove, n − 1 electrons in valence shell, Group n − 1
  • Ionisation energy: always mention nuclear charge, effective nuclear charge
4 Chemical bonding
  • 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
5 Chemical energetics
  • 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 !!!
6A Chemical equilibria
  • Kc is about concentration, not no. of moles
6B Acid-base equilibria
  • 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
7 Reaction kinetics
  • Boltzmann distribution: Legend, label Ea
8 Periodicity
  • Acid rain: SO2(g) + H2O(l) → H2SO3(aq)
    absorbed by moisture in air
  • NO generated in engine due to high temperature and pressure
  • NO reduced by CO

9 Organic chemistry

Nomenclature
  • Alkene = C=C bond but can contain other functional groups
  • Ethane-1,2-diol not ethan-1-2-diol
Presentation
  • For structural formulae of organic compounds after reactions, show resulting carboxylate ion together with anion: C6H5CH2COONa+
  • 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"
Distinguishing tests
  • 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 AgNO3(aq) (Obs) Cl white; Br pale cream; I pale yellow ppt
Oxidation
  • 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
Other reactions
  • Markovnikoff's rule: Rich get richer; poor get poorer
  • Double addition/substitution etc requires excess reagent
Others
  • 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
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Civilian life post-exercise
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[info]goh_wz
post-exercise

Mid-autumn karaoke!
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Saturday. We've had so many Jap karaoke sessions I've lost count. xD

Japclass karaoke 2009-10-03
Desmond insisted on a photo

This one was disappointing for me because out of 5 songs I prepared, 2 were not on the catalogue :'( 「算数チャチャチャ」 and 「虹色ラブレター」 would have made such great songs DD:
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!"
And then the other 3 that I sang, I'd only prepared them on the day itself, so I found it hard to catch the melody too. Maybe I shall repeat the songs I sang in the past next time!

Sec 2 geometry
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[info]goh_wz

Jon says (1:32 PM):
i think jodie's solution is correct
Wei Zhong says (1:32 PM):
same
i saw
haha arts student > 2 science students D:

Jon says (1:32 PM):
i sent to xinyu too
i also sent to my friend studying engineering or math or something in cornell
i feel so stupid
Wei Zhong says (1:33 PM):
so did they solve it ahead of jodie?

Jon says (1:33 PM):
heck no, they haven't solved it
Wei Zhong says (1:33 PM):
HAHA
this is so interesting

Jon says (1:34 PM):
i still feel so stupid =(
Wei Zhong says (1:34 PM):
i feel stupid too


(no subject)
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[23:44:09] Chang Xing: it was a bit nerve wrecking at first
[23:44:19] Chang Xing: like zomg what if i cant get the answer. going to get fired liao.
[23:44:25] Chang Xing: >_>
[23:44:29] Wei Zhong: hahaha
[23:44:40] Wei Zhong: and isn't it an ego thing too
[23:44:46] Wei Zhong: j3 le! still can't do sec 3 qn
[23:45:14] Wei Zhong: you just started is it
[23:49:47] Chang Xing: yeah
[23:49:59] Chang Xing: j3 is not an improvement over j2
[23:50:02] Chang Xing: its a regression
[23:50:04] Chang Xing: >_>

(no subject)
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Saturday. I must have appeared stupid asking the cashier how I could cash my items, when the Salvation Army only accepts donations for the things they sell at their Family Thrift Stores. But since I've already made the effort (and spent the $0.91) to travel down to the middle of nowhere, I might as well give the cashier my items anyway, even if I won't be remunerated. It's certainly a relief to get rid of stuff like the clock whose ticking I can't stand (silent sweep ftw), Aesop's Fables that my P2 brother doesn't want either, and the GEP 20th Anniversary shirt whose front is actually classy but whose back is just ugly.

Still, I think this is probably the last time I'm going down to get rid of anything other than perhaps clothing, which Cash Converters doesn't accept. Looking at the prices of the items yesterday, I think the things sold by the Salvation Army is not cheap enough such that most people (other than students of the Japanese School) would be willing to specially make a trip down to the border of an industrial area just to shop, and to put up with the gross lack of variety. Some items have their original price tag on them, and are blatantly sold by the Salvation Army for prices higher than the original price. It doesn't make economic sense for ordinary shoppers looking for things with the cheapest price—at a matching level of convenience—to shop there.

The Salvation Army is clearly appealing to people specifically wanting to help the cause. But even if I want to contribute towards the Salvation Army's cause, putting up with the hassle and time wastage of going down and then buying overpriced second-hand goods sold as-is doesn't seem like a very smart way. I'd rather get my items from the shopping centre, first-hand and with warranty, priced reasonably, and then make a GIRO donation.

With such problems, I have no confidence that the things that I donate would go off the shelf and be reused.


Thanks to the 37 which didn't come at 2.58 pm as iris promised, I took forever to reach home. Then it was a rush doing my final revision, as it were, before japclass karaoke, and then travelling down to Cuppage Plaza for karaoke at Cash Studio on Basement 2 with Celene, Warren and Jon :D

Although our music tastes were divergent, other than Jon we generally sang a lot of emo songs D: Without realising it I picked many emo songs to mug. And in any case, mugging 4 Japanese songs (all from the compilation I received from Ack and Fiona) was grossly insufficient for 3½ hours, so I sang Chinese songs too, the restricted database of the latter notwithstanding. It was fun spotting Jpop songs that I like, and I compiled a list on my phone so that I can mug them for next time. (Interestingly the list contains mostly 2007 songs, which suggests that Celene and Jon's consumption of Japanese music might have peaked around 2007 and 2008. Jon admits being somewhat out of touch with Japanese music nowadays.) I've also realised how familiar I've become with ほうき星 (Younha, 2005) through all the karaoke sessions with Japclass.

It's quite scary listening to Warren talk about how busy life in medical school is—after what is effectively only 7+ months of solid school, students are expected to know every single vein, muscle and bone in the human body; how the brain works; how the body works as a whole; medical ethics and laws; local and overseas healthcare systems; right down to how to skein information from medical journals; and a whole gamut of other things that he listed but I forgot. (I forgot to ask what they'll then do from Years 2 to 5.) To think that they said uni's supposed to be slack. And I can't imagine having my whole academic life revolving around just one thing, without the contrasting modules that other faculties get to take. But I also felt a tinge of envy for their being able to gain such detailed knowledge about our own bodies after such a short time. I think I'd be lucky to learn even 1% of that throughout my lifetime about my own body. Their lives seem even more enviable comparing the knowledge they'll gain in the next 7+ months with the knowledge I'll gain (or not gain) during the same period.

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