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Everything posted by hermanntrude

  1. i think all you an do is superimpose orbitals. for instance if you put an s-orbital in the same place as a p-orbital, you get an sp orbital. i guess ideally you would alter the factor for each by half to keep the scale correct
  2. hermanntrude


    I can't really sum it up in a post. It's quite in depth and also i don't know it very well. try wikipedia.
  3. hermanntrude


    you need band theory for metallic bonding. many courses skip that.
  4. the units of R can also be written J/mol/K
  5. there is one material which is totally indestructible. If you try to destroy it, it's only replaced by more and it gets more and more dense over time. Currently it covers nearly all of the earth's land mass and is expanding. it is of course, stupidity.
  6. ammonium hydroxide has never been isolated. it may form ammonium ions and hydroxide ions, but not ammonium hydroxide. we dont say that water forms hydronium hydroxide.
  7. i'd go for tungsten. Incredibly hard, massively high melting point. Probably rather brittle, though.
  8. actually ammonia, like water, is amphiprotic, meaning it can act as a base OR an acid. It can even autoionize like water: [ce]NH3 + NH3 -> NH2- + NH4+[/ce] The NH2- ion isn't a common one, though, and the equilibrium constant for the reaction above is about 10^-30. NH3 is much more likely to gain a proton (or give away its lone pair) than to lose a proton.
  9. You can certainly distil the coloring from water. However, the coloring is a nonvolatile solid dissolved in water. So when distilled it'd immediately be totally separated. I want to show that with two volatile substances, the mixture you get from the condenser is richer in the more volatile substance but not pure. The best I have so far is methanol and water, and setting fire to the more methanol-ly mixture. trouble with that is that it probably won't obey raoult's law because i doubt it's an ideal solution.
  10. true. That was one idea I had and as long as i steer clear of the 95% area there won't be any azeotropes. However, it'd be best if I could quantify it so I could calculate the concentration as a prediction beforehand. i'm thinking pH, but i don't know whether the more volatile acids form azeotropes
  11. I've been thinking of a demo I want to do to show the distillation fo two volatile substances. I'd like to find a pair of volatile substances which have different boiling points, no azeotropes (or at least none which will cause any errors), and here's the tricky part: they have to be easy to spot the relative concentrations. So the idea is I'll have a mixture, it'll be obvious (perhaps by smell, colour or pH) that it's got both substances in it. I'll distil it for a while and it'll then be obvious that the new mixture is more concentrated in the more volatile substance. Ideally, the concentration of one substance would be fairly easy to quantify, at least on a rough scale. I wondered if perhaps an acid in water might work, despite probably not being very close to ideal... or perhaps there's a coloured volatile liquid I could use? perhaps density would be an indicator? suggestions anyone?
  12. there is no deltaV needed in this equation. There is only one temperature required. you were given one. And the term "normal boiling point" refers to the temperature at which the vapor pressure is equal to 1atm. any help yet?
  13. if you review the work you must have done on gases fairly recently, you will find there is a relationship between a gases density and it's partial pressure (hint: try rearranging the ideal gas law). then you can use the C-C equation as you suggested.
  14. from the website that apparently no-one read:
  15. not sure what you mean by product/solution ratio. However, you can tell if you're overdoing it by first deciding exactly what "overdoing it" would entail (perhaps it doesn't matter if your solution is acidic anyway?) and then using a pH paper to test a drop at a time. If the solution is only slightly acidic or basic, a few good washes with water will get it closer to neutral, if that's what you desire.
  16. what solvent were you using? perhaps they just chose an oxidising agent which was soluble in your solvent
  17. ammonium hydroxide does not exist. But yes, what tartaglia said would be my guess too.
  18. the fahrenheit scale is amusing. It was based upon the freezing point of salt water (0°F) and the rectal temperature of a cow (100°F). Still more amusing, mr celsius, when he decided to make his scale, thought it'd be clever to make the boiling point of water 0°C and the freezing point 100°C. Immediately everyone told him how stupid that was and swapped it around.
  19. in the end, what decides whether a substance dissolves in water is the relative strengths of the intermolecular bonds between the substances. For instance, with salicylic acid, there are attractions between salicylic acid molecules which are very strong. There are also attractions between water molecules which are very strong. The attractions between a salicylic acid molecule and a water molecule just isn't strong enough to overcome the forces holding the pure substances together.
  20. the colour change is due to chlorine gas. Oxygen requires a fairly hefty overpotential, as does chlorine, so you usually get a mixture of both gases depending on the voltage and concentration of the salt. I know that if you use very concentrated salt and a 9V battery you get a LOT of chlorine (so much so i wouldn't do that indoors)
  21. many textbooks have a worked example of a system containing some gas which is compressed. The deltaH is calculated and the work done on the system is also calculated. First the compression is done in a single step and then it's done in two smaller steps, and the work turns out to be different for the two steps. If you have a large library nearby, I know there's an example like that in "general chemistry: principles and applications" by petrucci, herring madura and someone else too, 9th edition. However, it's probably in lots of other books in one other form.
  22. lucky, you sound like a dangerous person. You know a little, but nowhere near enough. Please stop doing experimental chemistry until you learn a bit more, for your own safety. by the way, bat faeces is not pure potassium nitrate by any means.
  23. Toadie, please don't answer people's homework questions for them. Give them clues on how they can do it for themselves.
  24. You cannot get sodium like this: http://www.scienceforums.net/forum/showthread.php?t=40177 There are ways to get sodium but they're all extremely dangerous, and of course sodium itself is pretty nasty too. As for HCl, again there are various ways, but this is not the way. However you are correct in saying you've made Cl2, chlorine gas. Be careful breathing around that stuff it can be quite harmful. One method for making HCl (which i don't recommend trying) is to fill a small testtube with H2 and Cl2 gases, and then expose them to a bright burst of sunlight. An explosion occurs and HCl gas is created. Obviously there are better ways but generally they don't start with chlorine gas.
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