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hermanntrude

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Everything posted by hermanntrude

  1. very cool, RH, I love the idea... can't wait to see the finished product
  2. it's very strong compared to anything this fellow is likely to have come across if he is forced to extract lithium from batteries rather than just buy it.
  3. here is a post I wrote on a non-scientific forum elsewhere, perhaps you'll find it interesting reading
  4. LiOH is a very strong base. There may be some interesting stuff you can do with that if you're careful.
  5. quantum theory has recently been removed from my syllabus, hence my dismissal of the 3D diagram as too complex
  6. very interesting diagrams, and very informative, but a little too complex to make a useful mnemonic for students, I think. In my classes I don't teach the 2-D diagram, mostly due to its inconsistencies and it having no real benefit to a student. I've often seen students who have written out the above diagram in an exam, only to use it completely wrongly to predict the wrong electronic configuration, where they could easily have gotten the right answer simply by looking at their periodic table (and even easier still by looking at an ADOMAH PT)
  7. it's tradtitional to only draw one conformer of any organic compound, unless one is discussing conformations specifically. Multiple conformers doesn't mean multiple products, since usually conformers interchange frequently over time except at low temperatures or when there is steric hindrance. The group you referred to is a tert-butyl group, not an isobutyl
  8. honestly, the ideal gas law might or might not help, but the clausius clapeyron equation is designed for exactly this situation: [math]\ln(\frac{P_{2}}{P_{1}}) = \frac{\Delta H_{vap}}{R}(\frac{1}{T_{1}}-\frac{1}{T_{2}})[/math] apologies for the non-greek spelling for delta, but latex wouldnt accept the symbol. Note that you're given the deltaHvap and T1 and P1 and P2. just solve for T2
  9. no it doesnt. the small p in pH represents the negative log base ten. pH = -log [H30+]
  10. hehehe that's much easier. but nowhere near as much fun!
  11. I did this experiment, mooeypoo, with my class of science students, and we got a value of about 2.3 x 10^8 ms^-1. I'm fairly sure we didn't do too much that was wrong, and although it might be a bit low, and of course the magnetron probably doesn't have the frequency quoted, I thought to myself "shouldn't the speed of light be slower in chocolate than in air anyway"? the speed of light in a medium other than vaccuum (oxymoron, sorry) is dependant upon the medium's density, hence we get refraction bending toward the normal upon movement from a less dense to a more dense medium and vice versa. The speed of light in water is about 2.2^8 m/s, so in chocolate, which has the same approximate density as water, shouldn't it be around the same value, roughly? I wonder if people have been biasing their results due to their "knowledge" that light travels at 3 x 10^8 m/s?
  12. I couldn't find a function to do this, so I used "ceiling" and "floor" together with "trunc", and some nested "if"'s to do it for me... now this is what I got: =IF((A29-(10*(TRUNC((TRUNC(A29))/10))))<2.5,FLOOR(A29,5),(IF((A29-(10*(TRUNC((TRUNC(A29))/10))))<5, CEILING(A29,5),(IF((A29-(10*(TRUNC((TRUNC(A29))/10))))<7.5,FLOOR(A29,5),CEILING(A29,5)))))) my question is... did I waste my time? Is there an easier way? Ceiling and floor round, but only in one direction, so you need the if's to determine which way to round the number. the nested truncs are just to get rid of the numbers at the beginning. The function is only designed to work on numbers between 0 and 100, for rounding students' grades to the nearest 5.
  13. I guess the density of the gas isn't very important, since whatever is produced need only be less dense than sea water. Perhaps even a liquid product would work, although I guess you'd need a fairly speedy ascent and also the ability to carry a payload...
  14. would the outside of the earth be exerting a gravitational force on you when near the centre? essentially slowing your fall?
  15. I think the roation of the earth is one of the "technicalities" we're supposed to disregard
  16. here's a link also here's an MSDS so u know the hazards you're dealing with.
  17. that video has been proven to be a hoax. It turned out they had explosives to cause the explosions, and caesium was not involved at all. Actually, there is a website somewhere with videos of five grams of caesium and five grams of rubidium being dumped into water, and surprisingly they're not as violent as you'd imagine. This is explained by the fact that 5 g of cesium contains less moles of atoms than five grams of sodium or potassium, since each atom weighs so much more.
  18. nevertheless, in some places it has caused accidents and has been banned in schools
  19. probably not, actually. what bothers me is that it's not you that's doing it. I know the nernst equation, but it won't help you if you don't know the concentration of the HCl or the two Cu ions.
  20. not everything can be entirely predicted by the book. You don't know the concentration of the Chloride ions or the concentration of the cupric/cuprous ions, so you can't predict the likelihood of a reaction. the "emf" values you refer to are only valid at standard temperature and pressure and at one molar concentration or, in the case of gases, one bar of pressure.
  21. the trouble is that things are a bit extra-confused by the presence of HCl. Adding oxidisers may make more than one reaction occur
  22. this is all excellent experimentation and I have to commend you However, I don't think you've totally understood the ferrofluid synthesis. the reason they synthesise the magnetite like that, in solution, is that they're trying to form a stable colloid, which won't precipitate (flocculate) over time. If you take your powder, which I have no doubt is at least 80 or 90% magnetite, and make a sludge with some oil or other solvent, it'll be magnetic, and act a little bit like a ferrofluid, but when all is said and done it won't be a liquid, or a colloid. At best it will be a temporary suspension. None the less fun for it, though, I imagine.
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