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Posts posted by woelen

  1. How do we work out the valencies of such radicals as [math]SO_4[/math]? Do most compounds have valencies or just radicals? I always thought that for something to have a valency it would have a desire to gain or lose electrons' date=' I cant see how a compound would do that... it just doesnt seem to make sence, once it is a compound it should be satisfied.


    Hope somebody can help me clear this up.[/quote']

    I just forgot something in my previous post. A radical also is a compound and it frequently also is a molecule. A radical is not that special. A compound is called a radical, if it has an odd electronic configuration. A well-known compound, such as the brown NO2 gas or the deep yellow ClO2 gas also is called a radical, while these molecules are stable enough to be prepared in macroscopic quantities and can be stored. In fact, I have made both gases in my home lab several times :D


    As a rule of thumb, you can assume, however, that radicals are very reactive compounds. A known ionic radical is the ion SO4(-). This can be prepared in minute quantities when a solution of a sulfate is electrolysed. Two ions SO4(-) can combine to the well-known peroxodisulfate ion S2O8(2-). So, where would you place the border between radical, compound and molecule?

  2. How do we work out the valencies of such radicals as [math]SO_4[/math]? Do most compounds have valencies or just radicals? I always thought that for something to have a valency it would have a desire to gain or lose electrons' date=' I cant see how a compound would do that... it just doesnt seem to make sence, once it is a compound it should be satisfied.


    Hope somebody can help me clear this up.[/quote']


    If you really want to understand, then have a look at the concept of molecular orbitals.


    In single atoms, electrons are in atomic orbitals (in laymans terms, something resembling orbits, but a good description can only be given by means of quantum mechanics), but when atoms combine to molecules, then part of the electrons are shared between atoms and they 'orbit' around over the whole molecule (better: they are distributed over the whole molecule). Molecules (or ions, or in fact any structure consisting of multiple boonded atoms) can certainly have a desire of electrons or want to get rid of electrons.


    An example is the following compounds:


    hydroxyl: OH This is a very strong oxidizer and really wants an electron. If it gains an electron it is changed to the the stable hydroxide and the newly gained electron is distributed over the whole OH(-) ion. So, one could formally speak of hydroxyl having valence 1, because it can make a single bond with something else. In practice, however, the valency concept is not used for compounds, but for atoms only.


    In general, the innermost atoms are confined to the atom to which they belong, but the outermost electrons are distributed over molecules or part of molecules. A very nice example is the benzene molecule C6H6. This has 6 electrons, which are distributed over all 6 C-atoms and one cannot say anymore which electron belongs to which atom. Other electrons are confined to just two C-atoms or one C-atom and a H-atom.

  3. I'm sure I asked this before' date=' but can't remember/find the answer.


    So, well, I can ask this several ways, complete the pattern:


    CaCO3 --> limestone --> calcium carbonate

    H2O --> water --> ______?


    It's not hydroxide which would be OH, its not a dioxide because there's only 1 O... so what is the chemical name (is that the right phrase?) for water?


    [i'][edit] In the title, I used a capital O and then it changes it back, dunno why, I've tried it 4 times now, it won't stay capitalised!!![/i]


    Have a look at http://www.dhmo.org/msdsdhmo.html ;)

  4. I beg to differ. The only way you can 'smell' something is if it is airborne and has volatalized. HOCl just simply will not be volatalized in order for you to smell it. HOCl and NaOCl are virtually the exact same thing. When in solution, an equillibrium exists resulting in the production of minor amounts of chlorine gas. The smell from a bottle of bleach is the smell of chlorine gas. There is no doubt about that. Hypochlorus acid is not a stable acid.


    I would say, try it (but be careful). There really is a difference!


    According to the book "chemistry of the Elements" by Greenwood and Earnshaw, HOCl is volatile and exists in the gas phase. Its solutions can be concentrated to up to 5 mol/l, but in that concentration, quite some HOCl exists in the form of Cl2O (Cl2O + H2O <--> 2HOCl, at zero degrees the equilibrium constant K = 3.5*10^(-3) mol/l). Its solutions really do volatilize and so they can be smelled.


    I agree with you that HOCl is unstable, but not to the extent as you suggest.

  5. at the second link i found indole and tetrahydrofuran.


    see' date=' that's confusing. indole is legal? people can just buy it and make any sort of tryptamine. and THF? great for certain organic syntheses[/quote']


    I is unbelievable what you can get from raw chemical photography suppliers as an individual (I am outside the USA, I read a lot about watched chems in the USA, but where I live that fortunately is not a severe problem - yet).


    Look at the list of chems I have ordered online in the last 7 years and which I now have in my home lab.



    I think that 75% of all these chems is from photography suppliers, and from that 75% a large part is coming from the two I mentioned earlier. In fact, some of the chems I do use for photography, but some I just ordered for playing with in my home lab.


    If I order chems, then I order many chems in one go and 10 - 100 gram per chem. That keeps costs acceptable and besides that, what is the use of having a pound of NaCN around, just for performing some experimenting? I do microscale experiments.


    If you are in for pyro, then the photography suppliers are not the place to buy from. Purity is high, but prices are too high for pyro-applications. I'm not a pyro-man, so for me it is exactly what I want.

  6. chlorine (VII) oxide' date=' Cl2O7 and anhydrous perchloric acid are exactly the same.


    and yeah, heat it or hit it with a hammer and it will decompose. but im talking about storage. if it's stored properly, it shouldnt be problematic.[/quote']

    Just stay away from Mn2O7. I once made this with a few mm3 of KMnO4 and a drop of H2SO4. I saw a faint violet vapor (it is volatile) and every second or two a tiny speck of light (these were dust particles from the dust of my room, touching the liquid and oxidized immediately). After a few seconds it suddenly went BOOM and I had many tiny brown droplets on the wall and on the table, on which I did the experiment.

  7. Chlorine smells exactly like bleach and like a pool because both household bleach and a well sanitized pool emit chlorine gas. (Due to the equillibrium of Cl2 + 2NaOH <=> NaClO + NaCl + H2O. ) So when you open a bottle of bleach, you are smelling a minute trace of chlorine gas. When you stand next to a pool that was just recently chlorinated, you are smelling a trace amount of chlorine gas.

    No, I don't think so. What you are smelling is not Cl2, but very dilute HOCl.

    Hypochlorite is a very weak acid and especially in swimming pools, where water pH is kept near neutral for obvious reasons, quite some HOCl is formed:


    ClO(-) + H2O <--> OH(-) + HOCl.


    Chlorine really has a different smell. Just add a few drops of bleach to dilute HCl and sniff the mix carefully. Really, it is quite different.

  8. how bout one where u put in reactants, and if necessary the calculator will balance it and show the products.

    Computing the products, given a set of reactants, is impossible with the current state of art of computers and the current precision at which the conditions can be modelled. The results frequently depend on the conditions as well. These computations require massive quantum mechanics computations over thousands or even millions of atoms in order to simulate a somewhat realistic macroscopic system.


    Balancing equations is another thing and is not that difficult. I've written a program in C, which does that for you, by computing an integer null-space of a certain matrix. The program gives all possible reactions, given a set of reactants and products. Look at



    However, YOU are the one who must tell the program what are the reactants and the products. Shit in ==> shit out! The program just helps you with the tedious and error prone math.

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