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Everything posted by MulderMan

  1. Usually depends on who is setting your test! Some people like the arrows to finish at the middle of the bond, and some like them to finish at the other atom. The key things are arrows should start from a lone pair, or a bond, i.e the source of electrons. They should also be CURLY, straight arrows are for use in dative bonding (think inorganic metal-ligand). Once you have done a few of the more basic mechanisms, if you are given two reagents in an exam it becomes a sixth sense to know how they will react! Know your electrophiles and nucleophiles!
  2. Think of the units: c (specific heat of soln): J g^-1 K^-1 m (mass of soln): g ΔT (change in temp): K So, looking at the units, multiplying c by m and ΔT, you are left with the the energy change (absorbed by the soln), in Joules.
  3. MulderMan


    Whats the question? Just gas law ones i presume?
  4. First one dunno. The second one is phenylethanone, i.e a ketone. Ketones resist oxidation via tollens reagent as they done have that spare hydrogen like with aldehydes. Technically you can oxidise ketones using manganate (VII), but thats another story. So, in short the solution will stay colourless.
  5. Dont have a clue about the first one, Ive never dealt with more than one phenyl.. The second one is an alcohol, so draw the structure out fully, and find the longest carbon chain. Then follow the nomenclature rules! Post your try, and ill check. Nomenclature can be tricky if you cant think in 3d! Ill leave it to someone else to give the homework lecture..
  6. Oh... you do organic chemistry at that age?!!! Thats crazy. I cant even think what I was doing in science at that age?! Hmm..
  7. What age/level are you at? A few things to look up: Functional groups (and bonding rules): -alkenes -alkanes -alkynes -amines -alcohols -aldehydes -keytones -nitriles -ethers -esters Nomenclature Isomerism (functional group, positional, geometric, optical) Mechanisms -nucelophillic/electrophillic addition/substitution Aromaticity Spectroscopy (n.m.r., IR, mass spec) Tests for organic compounds... CURLY ARROWS!!! and ELECTRONS Haha, theres alot of things! Thats pretty much the spec. for circa 16-18 year olds, or so I should think/hope! Once you start to learn the basics, like bonding rules (i.e. carbon=4, oxygen=2 etc), nomenclature (the naming system) and basic mechanisms, and the concept of moving electrons with curly arrows you are set!
  8. The chromic acid test is for alcohols isnt it? Why dont you just do the 2,4,D again, and look up its melting point of the hydrozone in a data book. Thats what Ive been taught anyway...
  9. Might be worth looking up the born-haber cycle aswell, thats what we've been using in class of late for working out ionic bond enthalpys. Much like hess cycles but with alot more specific enthalpy changes!
  10. 1 mole of carbon atoms will have a mass of just over 12 - i.e its atomic mass. The general conversion formula for this is: Moles = Mass (g) / rmm/ram where are you getting the 9.8 from?
  11. Chemistry all the way! I suppose I'm an A Level biologist as well, but that doesn't count...
  12. The XTi/400D is a quite good starter dSLR, but you will definitely have to expect to buy some decent lenses with them as Mag said. You wont really get far with the 18-55 kit lens!
  13. MulderMan


    Just applied to join, although apparently I don't appear to be musically compatible with any of you!
  14. So who's on the countdown?!
  15. In all fairness the whole course. I got an E for C1 in January, and I just can't seem to be able to do a lot of any of C2 or S1. Guess its just a case of practice, practice, practice?
  16. Any ideas on how I can actually learn this, and pass it within the next week or so?!
  17. Is this A level, or GCSE, i.e do you want an explanation reffering to concentration gradients, or water potential gradients?
  18. There is probably an American centre registered to allow you to sit a GCSE, or IGCSE, but the use of it as a qualification to you, and the fees incurred probably outweigh the benefits. You could always sit a past paper and grade it yourself to see what equivelant level you are at?
  19. Resistance of a wire!!! That ones my favourite, just ask if you want more information. What exam board are you doing it on?
  20. I always used to get confused with this when calculating enthalpy changes, but as said above there is a same division of the scale. Except it you want to convert from C to K then you +273.15
  21. Fructose and gluclose join togeather in a condensation reaction, releasing a water molecule, and a surcose molecule. C6H12O6 + C6H12O6 --> C12H22O11 +H2O Then you can work out the molecular weight by multiplying each atoms Ar with the number of atoms are there, and add the values up for a total Mr. I.e Ar: C=12 H=1 O=16 (12x12) + (1x22) + (11x16) = etc
  22. The test we have always learned in chem is to see if it will light a glowing splint.
  23. Electron affinity is the energy given when an electron is gained by a neutrally charged atom, in the gasous phase, becoming a negatively charged ion. The trend increases across a group, and up a period, just like with the first ionisation energy.
  24. Generally speaking, a bond is polar between two atoms with a eneg difference between 0.5 and 2.
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