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Everything posted by hermanntrude

  1. you're halfway there. Most of the answers require you to know Kp to find if they are true or false
  2. i suspect it's to do with the denatured alcohol. it usually contains isopropanol and methanol... perhaps there's a reaction possible with IPA?
  3. also, a note to imp, a substance doesn't have to contain H+ to be acidic. Look up lewis acids and bases.
  4. i'm gonna test mine today with a stronger magnet. When i said flocculate i meant AFTER synthesis, not during. I wonder how stable the colloid is. no spiking. I know where i went wrong, though. I doubled my reactants but not the volume of the solvents, so i'm getting a lot of precipitation/flocculation.
  5. the reason ethylene dichloride has the same beginning to its name as ethylene is probably that the reaction was first performed before people fully understood the reaction. Perhaps they thought it was ionic, since the name seems to suggest that.
  6. two points: 1) you have two data which you labelled "volume of distilled water", one of which is 2 mL and one is 0.0 mL. Which is it? 2) the question is badly worded, since it tells you that the rate of the reaction is the change in concentration of the hydrogen peroxide per second. The IUPAC reccomendation for measurement of rates is the negative of the change in concentration of a reactant divided by the stoichiometric coefficient. In other words, the change in concentration of hydrogen peroxide is actually negative of a double the rate, not the rate itself. to find the rate of decomposition of hydrogen peroxide, divide the change in concentration by the time. If you want the answer in moles/litre/second, divide by seconds instead of minutes.
  7. it's a difficult thing to do, for sure. Practise, practise practise, and learn the mechanisms in your textbooks. Never forget what electrons are and how they behave, that way you can often tell where they might come from and where they might go to. Also, don't forget that in many of the complex mechanisms, the key step is when four or six electrons move in a circle (an aromatic transition state).
  8. I got some very strong ceramic magnets at Canadian tire. When i get back to my college, assuming my ferrofluid hasn't flocculated, i'll try it out.
  9. yes these are about a quarter inch diameter. I guess i'll have to suck it up and order a larger one or get one out of a hard drive
  10. not entirely true. Some reactions are independant of the reactant's concentrations. Temperature is also a slightly cloudy issue. All reactions are equilibria, but some equilibria lie so far shifted to the products that we consider them to be one-way reactions. The equilibrium constant is dependant upon temperature. Look up the Arrhenius equation.
  11. OK my second attept worked much better. I did as ironious suggested and added a ton of steel wool to my aliquot of FeCl3 and left it for a day to react. After filtration it was a lovely green colour. My magnetite was completely black this time instead of dark with an orange tinge, and my parrafin solution at the end was definitely magnetic, BUT... no spiking :'0( very disappointed, although i might be able to improve it after letting it settle and decanting it again, perhaps diluting half of it, it's very viscous. Also I'm think that a large steel magnet might be better than a small neodymuim magnet
  12. well done, ironius. Tell me, how did you find the reduction of FeCl3 to FeCl2? I found that just adding steel wool and stirring didn't change the colour much at all. It's sposed to go green but it didn't for me. By the way "kerosene" which is paraffin in real life, definitely doesn't mix with water. It might temporarily combine in a weird colloidal suspension under some conditions but if you leave it to stand it will always separate
  13. There is a paper by G. W. Whitesides called "how to write a paper" or something along those lines. It doesn't go into a lot of detail about syntax but it IS extremely helpful when writing a paper. Correct english is always the preferred syntax, and in this case you are correct that ideally you would use the present tense, since you're referring to something which STILL HAS three variables, rather than something which used to have three variables. You may run into opposition with this, since a lot of people have been told that all papers should be written solely and entirely in the past tense. In fact the past tense is used in general but when grammatically correct, future and present tense are allowed. To avoid putting past and present tense in the same paragraph, perhaps consider splitting into two paragraphs. there is no rule that a paragraph should be long.
  14. well my first attempt didnt work. I found that making FeCl2 from FeCl3 and steel wool didn't work out. So I made some using HCl and iron filings, but i wasn't too careful about concentrations and I also used concentrated ammonia instead of dilute, and my magnetite flocculated. I think a magnetic stirrer bar might have been a mistake too. Attempt number two will be made shortly
  15. you did the right thing, scientifically. Bar graphs are far rarer in science than line graphs, and you can see why. Often, as in this case, the gradient of the line which interpolates between actual data points is significant in some way. With a bar graph, the line isn't there and so the gradient cannot be seen. Of course... you CAN draw a bar graph and plot a line on top, i've seen that done...
  16. there IS a relationship between concentration and rate, AND there is another relationship between temperature and rate. Your experiment design involves changing both factors at once. perhaps you should be investigating the effect of temperature separately from the effect of concentration. I figure you'll need much more than 2 test-tubes
  17. each letter is worth 15.538461538461538461538461538462 That way, a-m =202, n-z = 202 also. This is one possible answer which is not forbidden by the terms of the question.
  18. pH meters are famous for being unreliable. They tend to get easily put out of calbration and are way too sensitive to things like temperature, movement, proximity of the glass of the beaker in which the reading is being taken. personally i'd reccomend either using pH paper or a very expensive pH meter.
  19. that's the one i use to teach my lower stream, students. It's very good, but a little shallow in detail in places. My advanced chemistry students use general chemistry principles and modern applications by petrucci, harwood, herring and madura
  20. bromine is a liquid, and much more dense than water. I expect you all know this, but bromine is nasty stuff. I've worked with it before and it can RUIN people's lungs. Be careful. Read the MSDS here
  21. think about the amount of charge on NaCl and the sizes of the ions, then try the same with sucrose. Look up charge density.
  22. safe as anything. No need for any concern on that, since i didn't use anything they wouldnt have had at home. I considered doing the thermite reaction but decided it's just too dangerous. Also considered buying some rubidium and decided against it. Next on the list might be a balloon full of hydrogen.
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