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  1. histephenson007

    Chemistry 42....how did it go?..expected GT

    how about the oxidation with Potassium Chromate? What was the Ecell and the equation. And the concentration of A
  2. histephenson007

    People out there......please read this. It's a sad story about my chemistry practicals.

    Just last year, I messed up my whole ion test question and did my p1 and p2 well. At the end, I got A (92) for AS level, with 2 As in p1 and p2, but a D in p3. So, don't worry ;)
  3. histephenson007

    Hey, what was the isomer for D in the lawsone question?!

    Hey, what was the isomer for D in the lawsone question?!
  4. histephenson007

    Chemistry 42....how did it go?..expected GT

    The answers for the first question in Section B were : Van der Waals force Disulphide bonds Hydrogen bonding Hydrogen bonding Right?! And, what was the equation for Potassium Chromate oxidising Compound A to lawsone?
  5. histephenson007

    Chemistry 42....how did it go?..expected GT

    Juglone doesn't have an ester, but compound D does.
  6. histephenson007

    Chemistry 42....how did it go?..expected GT

    Definitely A* :)
  7. histephenson007

    Chemistry 42....how did it go?..expected GT

    yea, that was a hard question. I was working on it for the last 15 min - - And couldn't come up with a chiral centre, so I just drew the mirror image of the whole thing
  8. histephenson007

    Chemistry 42....how did it go?..expected GT

    Quite easy :)
  9. histephenson007

    Chemistry P4| A2 only

    Think of it as a free-radical substitution reaction and add chlorine on each Carbon atom. Beware with the left ones.
  10. histephenson007

    Chemistry P4| A2 only

    First, we need to get the Ka value from the pKa .. pKa=-log(Ka) So, Ka = 10 ^(-4.76) The acid equation is : CH3COOH <---> (H+) + CH3COO- So, Ka = ([H+]*[CH3COO-]) / [CH3COOH] Re-arranging the equation: [H+] = (Ka*[CH3COOH]) / [CH3COO-] But, we don't know what [CH3COO-] is, So, we hav to...
  11. histephenson007

    Chemistry P4| A2 only

    For 7.c)i) You'll hav to use this formula : No. of Carbon atoms = [(100/1.1) * (M+1/M)] . So, you'd get 3 Carbon atoms. ii) There was M+2 peak present which had similar height to the M peak. This sort of peaks can only be formed with Bromine, because in the booklet, it is the only element...
  12. histephenson007

    Chemistry P4| A2 only

    which part is not working?!
  13. histephenson007

    Chemistry P4| A2 only

    There is no Q3 i) ii) ... do u mean Q3. d i) ii) ??? (In that case, the only possible solution we could agree on was to try the trial and error method..... :sick: ) For Q4 c) Because we have to find out which one of these oxidation processes are likely to occur, we need to find out the E cell...
  14. histephenson007

    Chemistry P4| A2 only

    yes, you can check with Standard electrode potentials if you want. Usually, instead of O2, halogens (except Flourine) Cl2, Br2, and I2 get released when electrolysis takes place in aqueous solutions.
  15. histephenson007

    Chemistry P4| A2 only

    histephenson007 said: ↑ http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_42.pdf 3.d)i) dafuq?? we should find out the answers by trial and error method or what/??? also include ii) plz Is everyone sure that the only way to solve this is...
  16. histephenson007

    Chemistry P4| A2 only

    THANK YOU VERY MUCH. That solves it :D
  17. histephenson007

    Chemistry P4| A2 only

    In the markscheme, the value for lattice enthalpy is just directly given as a positive value. That's why I got confused. AND, in pg 225 of the A level Chemistry book (look at the graph). But what u say makes sense, its opposite to hydration enthalpy, so positive. I'll just hav to go with...
  18. histephenson007

    Chemistry P4| A2 only

    got it, thanx!
  19. histephenson007

    Chemistry P4| A2 only

    http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_42.pdf This paper is kinda tough. Does anyone know the GT for this? Meanwhile, my questions from dis papers : 2.b) Can someone explain the calculations. Again, I've said this before...
  20. histephenson007

    Chemistry P4| A2 only

    Man, I was gonna answer this question long time ago, but saw propane and thought that this was something new. but...phew nothing new :D
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