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  1. S

    Circle Geo

    i think this question was from the 2002 HSC (Q4?). simson's line.
  2. S

    UNSW school maths comp

    if u haven't already noticed, i'm always on the right hand side of every equation :p
  3. S

    UNSW school maths comp

    no turtle prolly jus needs to know when we need to vacate the clancy
  4. S

    how do you remember the activity series?

    hmm last time i checked, beryllium was less active than calcium.
  5. S

    Advanced 3-Unit Questions

    go get a tutor if u want a better use for your time. time is money
  6. S

    Testing for Cations: Flame Test

    no you're not ignorant; it hasn't been answered yet anions also absorb / emit energy. the difference is that the cations emit energies corresponding to the visible-light part of the EMR spectrum, whilst anions emit energies corresponding to higher (perhaps UV) part of the spectrum and thus...
  7. S

    integration: partial fractions question

    multiply top and bottom by 1 + tan(x/2). i jumped a step and expanded the denominator already.
  8. S

    integration: partial fractions question

    tan(45 + x/2) = [1 + tan(x/2)] / [1 - tan(x/2)] = [1 + tan(x/2)] ^2 / 1 - tan^2(x/2) = [1 + 2tan(x/2) + tan^2(x/2)] / 1 - tan^2(x/2) = * let t = tan(x/2) then * = 1 + 2t + t^2 / 1 - t^2 from t-results, we know that 2t/1 - t^2 = tanx, and 1 + t^2 / 1 - t^2 = 1/cosx = secx so tan(45 +...
  9. S

    help me about first-hand investigation,plz

    geez unless they ask for a quantitative analysis, i reckon you can get away with using the keywords "high" and "low", in describing solubility.
  10. S

    Chemistry Horror Stories

    i've recently discovered where the store of calcium carbide is in our school muhuahaha
  11. S

    carboxylic acids

    but won't the Na+ ions left behind make the muffin basic? the only anions that could possibly be left behind is the hydroxide ion.
  12. S

    Chemistry Horror Stories

    next time u pick up beakers when there are beakers with strong acid around: get a paper towel and wipe it dry. a poorly-documented laboratory test for conc acid is it discolours the paper. conc sulf turns the paper black, conc nitric turns it brown.
  13. S

    Chem Quiz

    like, real solid stuff like calculations, etc. not arty-farty environmental and social issues with batteries and crap we get for HSC
  14. S

    questions...

    you've diluted the acid when you added the silver nitrate in. that's why [H+] is decreased and hence pH rises
  15. S

    Reflux

    oh yea.... oops gee my maths is so crap now i can't count to 3 stoopid med it's brainwashing me
  16. S

    Reflux

    it's the same thing
  17. S

    Reflux

    hazard warning: methanoic acid is found in all soft drinks in high concentrations! its reduced form, methanal (a.k.a formaldehyde) is a known carcinogen (cancer-causing substance)!
  18. S

    formation of esters

    the oxygen in the released water comes from the alkanoic acid, but the hydrogen, in truth, can come from anywhere (except hydrogens bound to carbon). if you do an experiment where you have deuterium (heavy hydrogen) on the H of the OH in the alcohol, and dissolve it in water, and let it come...
  19. S

    Cyclohexane // Hexane

    well, the thing with 660 molecules of Br2 to every molecule of HOBr (OBr- anion) is that the argument will work if u assume that both species are equally likely to react with the double bond. but in terms of mechanisms, the reason why the conq chem is dodge is that HOBr is actually H+ and...
  20. S

    Cyclohexane // Hexane

    aqueous bromine is an equilibrium mixture of Br<sub>2(aq)</sub> and HOBr (formed when Br<sub>2</sub> reacts with H<sub>2</sub>O to form HBr and HOBr). But conq chem is wrong. mechanistically, it is Br<sub>2</sub> that reacts with the double bond. in short, just write Br<sub>2</sub>
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