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Everything posted by woelen

  1. Easy: Add KOH to HNO3. KOH + HNO3 --> KNO3 + H2O If you intend to do this, be careful. It is a VERY exothermic and violent reaction, especially if solid KOH and concentrated acid are used. Of course, doing this is a waste of chems. KNO3 is much easier to obtain than HNO3, so normally one does not waste his/her HNO3 on a reaction like this.
  2. Are you sure that is valeric acid . Isn't it an ester of valeric acid? If I had to drink tea with some valeric acid in it, I probably would have to vomit because of the really disgusting smell (and probably also taste).
  3. Lime water is a solution, containing Ca(2+) ions and OH(-) ions. OH(-) ions react with CO2 as follows: 2OH(-) + CO2 --> H2O + CO3(2-) With calcium ions in the water a precipitate is formed: Ca(2+) + CO3(2-) --> CaCO3 (ppt) So, bubbling CO2 through lime water produces a white cloudy liquid. If a lot of CO2 is bubbled through this, then a white precipitate is formed, which after some time settles at the bottom. You can even demonstrate that you exhale CO2, if you breathe out some air and bubble this through lime water.
  4. First, of course, if it is not a liquid at room temp, then it is not water. If you want to test whether a sample contains water, one can heat it and collect the vapor. Next, one can start adding certain anhydrous salts (e.g. anhydrous CuSO4 or anhydrous CoCl2). Anhydrous CuSO4 turns from white to blue on addition of water or when it is placed in a stream of humid vapor. Anhydrous CoCl2 turns from blue to pink, when water is present. These just are some thoughts, but certainly there are many other compounds, which can be used to detect water. I would expect it to hydrolyse and the main reaction to be PBr3 + 3 H2O --> H3PO3 + 3HBr The HBr dissociates further in water, forming H(+) and Br(-). H3PO3 also is an acid, it is a fairly weak diprotic acid and can dissociate up to HPO3(2-).
  5. In fact, there is no real upper limit on the size of n. In practice, however, it will be more and more difficult to create a pure compound. For very large n you will get mixtures, which are solids. Another example of a huge molecule is graphite. It is a layered structure of carbon atoms, arranged at the vertices of hexagons. Think of an infinite plane of benzene rings, where the edges of the rings are shared with the neighbouring rings, just as in naphtalene. Diamond also is a macro molecule, consisting of carbon atoms, bonded to each other in a 3D structure (as far as I remember, each carbon is bonded to 4 other carbons at the vertices of a tetrahedron). In fact many compounds can be regarded as single large molecules. In practice, there are defects and the molecules are not really macro, but molecules of millions of atoms are quite common. In very pure crystalline solids, the number of atoms, fitting in the ideal pattern can easily exceed billions.
  6. Indeed, I agree with jdurg. Gallium has a very low melting point for a metal, but it remains liquid up to a very high temperature (as far as I remember to over 2200 degrees centigrade). So, no fear for vapor, unless you heat the stuff to 2000 degrees or something like that and you sniff above the hot liquid . Gallium, however, does stain. I have some of it and everything, which is touched by it becomes wetted by it... horrible! I also have mercury, and up to now I only used it once in a very controlled way in a small experiment. The toxicity of that indeed is of a TOTALLY different level.
  7. No, that is not possible. The acid HClO3 is not stable and only exists in dilute aqueous solution. On concentration, it decomposes, giving Cl2, H2O, ClO2 and O2. Under the combustion conditions with plenty of oxygen available, the only really stable chlorine compound is HCl.
  8. Metal etching can also be done very well with a mix of hydrogen peroxide and hydrochloric acid (muriatic acid). Hydrogen peroxide is easy to obtain (3% concentration, but for hair bleaching 10% is available also). You can concentrate 3% H2O2 to 10% easily yourself by freezing the liquid for half the volume and keeping the liquid part. Repeat this two times. Mix 1 part of 10% H2O2 with 1 part of 30% HCl and you have a perfect metal etching mix. It eats rust and it also (slowly) eats metal. Although this mix is quite nasty, it is not nearly as nasty as concentrated nitric acid and the ingredients are much easier to obtain. Do not store this mix in a closed bottle, as it slowly decomposes and may lead to high pressure. If you store it in a loosely capped bottle, then store it in an old barn or something, but not inside your house. The fumes are really corrosive and you would not like these to have in your house.
  9. I'll give you some cool experiments, but please be very careful with H2O2 (35%). This is quite nasty stuff, for your skin, and it decomposes very easily. If you get some on your skin, then it'll cause almost immediately severe irritation of your skin (white stains, which itch and sting really badly) . Take 3 to 5 ml of 35% H2O2 and add a spatula full of solid calcium hypochlorite (the stuff, used in swimming pool). Do this in the dark. You'll see a red ghostlike glow (you get singlet oxygen, which gives a red glow, when it is converted to triplet oxygen). Do NOT scale up this experiment! Hydrogen peroxide forms beautifully colored peroxo complexes with many transition metal salts: Concentrated H2O2 can be used to make concentrated solutions of copper (II) chloride: Add some copper wire to 30% HCl. It just needs to be covered by the acid. Carefully drip in some H2O2 (35%) and swirl. Repeat, until all copper has dissolved. With the copper (II) chloride you can do more nice experiments. Do this outside, because quite some noxious fumes of HCl and also some Cl2 are released. Take 2 ml of 35% H2O2 and add a few crystals of KMnO4. You'll see an almost explosively violent decomposition. A lot of steam is produced! Quite spectacular, but please please do not scale up this one. Having too much H2O2 may cause the hot stuff to be swirled out of the beaker/tube! Have fun, and stay green .
  10. A well known method for reducing the amount of free Mg(2+) and Ca(2+) ions is the addition of a small amount of calgon. Calgon, a.k.a. sodium hexametaphosphate, coordinates to the calcium and magnesium ions. The ions are not removed, but they are not free anymore. Per example, they cannot form a precipitate with soap or detergents anymore and their adverse effect is reduced effectively It might be interesting to do the EDTA titration with plain tap water and with tap water, in which is pinch of calgon is dissolved. I would suggest you discuss this with your teacher. Yet another technique for reducing impurities in water is by means of certain membranes or filters. These membranes are constructed, such that water molecules can go through them, but the calcium ions not. However, for more details on this, please go to a library, because I cannot give you any sound advice on this.
  11. Zking786, you received multiple replies/warnings now. Did you get the message? STOP WITH THIS EXPERIMENT unless you change your setup . We would like to see you in this forum next month also .
  12. I completely agree with jdurg! Even, when not confined, a perfect mix of H2 and O2 will explode violently on ignition. Just to impress yourself, perform the following experiment. Take a tub, full of water and put in some soap. Take a few ml of a perfect H2/O2 mixture (not more, just a few ml!!!!!) and bubble this under water, such that you get some bubbles with the gas mixture at the surface. Before the bubbles pop and break apart, light them with a cigarette lighter. You'll be really impressed by the loud BOOM of just a few ml of unconfined gas mixture! If you have done this, then you'll certainly redesign your electrolysis device. You simply MUST collect the O2 and H2 in separate chambers if you do not want to blow up yourself!
  13. In fact, I am quite pessimistic about this one, especially if you have concrete bricks or tiles. These absorb some oil and it will be really hard to get it out. Using some VERY hot solution with NaOH and detergent may help a little, but for the rest you'll have to be patient and let nature do its job slowly. Beware: Be very careful with hot NaOH and its solutions. That stuff is really bad for your skin and causes instant destruction of your eyes, when you get a splash in them!
  14. Mix an excess amount of ammonium chloride with copper sulfate and then add an excess amount of NaOH. Observe the deep royal blue color (this can also be done by adding excess ammonia to copper sulfate). You get a complex ion [Cu(NH3)4](2+). Mix a few grams of ammonium chloride with a few grams of sodium hydroxide in a LOOSELY capped glass bottle and put a few drops of water on the mix. You'll get a fairly vigorous reaction (not extremely violent, but nevertheless, quite vigorous) and evolution of a gas and quite some heat. When the reaction is over, put the bottle upside down in a tub, filled with water and take away the cap. You'll see the water sucked into the bottle quickly. The ammonia gas quickly dissolves in water. Beware: the latter experiment must be done outside and be sure not to get any sodium hydroxide on your bare skin! That stuff eats skin quickly, especially if it is warm. Do not use more than a few grams, do not scale up!
  15. What you are saying here is NOT correct! Your reasoning is not valid. You cannot simply add up the acid concentration to the concentration of 10^-7. Try this for [HCl] = 10^-7. With your reasoning you would have a concentration equal to 2*10^-7, but this is false. The real concentration of H(+) will be 1.618*10^-7. I'll leave it as an exercise for you to explain this value.
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