woelen

Please be a little more clear. What do you want to know precisely?

Another way of proving such things is called by induction. Show that it is true for 1 or 2. Assume that it is true for n. Then show, using the assumption that it is true for n, that it is true for n+1. For n = 1, this obviously is true. Now, assuming it is true for a certain value n, we evaluate the sum for n+1. The sum for n+1 can be written as the sum for n + one term: n² + (2n+1). It is clear that this equals (n+1)². This is the proof. ------------------------------------------------------------- This kind of proofs is not useful of course if you don't have a clue what the actual sum is, but in many cases, one has an answer (either found by means of some other ingenious way, or simply given) and then this is a very easy way of proving.

Well, that gives a very good indication. If no carbon is in it, then it is inorganic. If there is carbon in it, then chances are good that it is organic, but not all carbon-compounds are organic (e.g. Na2CO3, CO2). The borderline between organic and inorganic is somewhat fuzzy. Na2CO3 is considered inorganic. NaCN also is considered inorganic, but some people think of it as an organic compound. Na2C2O4 (sodium oxalate) usually is considered organic, but there still are some people, who regard this as inorganic. Anyway, if you see a formula with a large number of C-atoms, H-atoms and some other atoms, then you are almost 100% sure that it is an organic compound. Because of the fuzzy border, the distinction organic/inorganic is abandoned more and more. We simply speak of carbon chemistry, just as we can speak of sulphur chemistry, chlorine chemistry, etc. The term 'organic' stems from the period that people believed that certain compounds only could be made by living organisms, but soon a synthetic pathway was discovered for making thiourea from inorganic compounds only. Na2CO3, C, N2 ---strong heating--> NaCN + crap NaCN, S ---heating--> NaSCN NaSCN + NH4Cl ---> NaCl + NH4SCN NH4SCN --->heating---> H2NC(S)NH2 An organic compound, made from inorganic materials only.

The element itself is not that important, what is important though is the scientific insight obtained by doing this kind of experiments and by studying the properties of the newly created atoms (such as halflife time and the type of particles, created when it decays). This is fundamental science, and fundamental science IS important. If we stop doing fundamental science then sooner or later all technological progress will come to a halt. Rexus, your remark shows that you are not / will not be a real scientist .

Copper may be somewhat oxidized at its surface, but it hardly can be called a reaction. You will get copper (I) oxide and copper (II) oxide, in a very thin layer around the copper metal. The inside does not react. The flame can also reduce some of the oxide back to copper. The hot gas is strongly reducing.

http://www.wfvisser.dds.nl/EN/kclox_EN.html

I doubt that you have the pure substance. The pure substance (a quaternary ammonium salt) is a solid, which dissolves in water as an ionic salt. You most likely have a solution, which contains 1 to 2% of the substance, probably together with some other quaternary ammonium salts. Quaternary ammonium salts are toxic to humans, but not insanely toxic. Here is a link to an MSDS of a product, containing around 15% of quat. amm. http://www.pharmacal.com/MSDS/US/MSDSQUATPV15.pdf The LD50 for rats of the solution is between 1 and 2 gram per kg of body weight in general. As with many chemicals, a single exposure to a small amount of this is not a problem. It hardly ever happens that a person gets a lethal dose at once of a certain chemical. You have to be careful not to be exposed to this on a regular basis with small quantities. Long-term low-level exposure may be harmful.

The most dangerous experiment, mankind is doing, is changing the climate on earth, modifying the CO2/methane content of the atmosphere. The effect of this experiment we all will experience in the next 20 to 50 years.

Yes, it is a redox reaction. Chlorine goes from oxidation state +5 to oxidation state -1. Oxygen goes from oxidation state -2 to oxidation state 0. KClO3 in fact oxidizes and reduces itself at the same time.

Yes, I agree with you jdurg, but as I told before, the people must also be told that they are studying simplifications, without actually going into detail about the more complicated and intricate things. That is the thing which I miss in your story.

It is not even important what the precise reaction between tin and H2Se is. The only thing, what matters is that the Se apparently is taken up by the tin and what remains is H2, and most important, for one molecule of H2Se you also get one molecule of H2. As long as there is sufficient tin, you would not need that reaction equation for solving this problem.

In a basic solution, you won't have CO2(g), you'll get carbonate ion instead. The two half reactions are: C2O4(2-) + 4OH(-) ---> 2CO3(2-) + H2O + 2e MnO4(-) + 2H2O + 3e ---> MnO2 + 4OH(-) With this you should be able to write down the total ionic equation for this redox reaction.

I only agree partially with jdurg. I have no objections against the use of simplifications, but one should also be told that simplifications are used. Nowadays, pupils think that this is the whole story, simply because no one tells them there is more to say about this.

Unfortunately ammonium perchlorate is very hard to obtain. It is a regulated chemical, because of its strategic importance. For the home-chemist/rocketry hobbyist, KNO3, mixed with suitable reductors, is the way to go, forget about ammonium perchlorate, I don't have it, and only few home chemists have it.

Of course, if you mean eating or inhaling them, then YES! But if you mean experimenting with them, then I say NO! Bromides are quite safe for experimenting. Bromine is another matter.

I do not fully agree with encipher. Metals with such high charge, usually are not forming fully ionic compounds anymore. For example, I certainly would call FeCl3 not purely ionic, in fact, it is quite covalent (e.g. it dissolves in acetone without problem). FeCl3 is a black fairly volatile solid, which dissolves in many organic solvents. The compound PbCl4 really is covalent. AlCl3 also is a covalent compound. The higher the oxidation state, the more covalent the compounds. Purely ionic compounds only exist of +1 ions (e.g. alkali metals), +2 ions (the heavier earth alkali metals, combined with very electronegative elements) and some more complicated systems with ions, which are consisting of multple atoms (such as ammonium, nitrate, sulfate, etc.). Even in the latter class, many compounds are partly covalent. So, NiSO4 is an insoluble mostly covalent compound, while NiSO4.6H2O is an ionic compound, easily soluble in water.

In reality, the p-orbitals are perpendicular to each other, so it makes sense to speak of x, y and z orientations, but the choice of which is x, y, and z is arbitrary. So, the answer of encipher, with two electrons in the p-x orbital and one in y, and z, could also be 2 in any other orbital and one in the remaining two. For practical situations, however, the abbreviated notations, disregarding the x, y and z orientations is used frequently.

Make a very fine powder of the KNO3 and add that to the acid and heat a little bit. Part of it will dissolve and your white solid, which does not dissolve is not only KNO3, it also is KCl. This mechanism works somewhat better with NaNO3. NaCl is really insoluble in conc. HCl and if the NaNO3 is very finely powdered, then most of the nitrate ions is replaced by chloride ions in the solid, but also here, part of the nitrate does not go into solution.

None of these chemicals burns. They cannot burn. They can give color to a flame, but only in the presence of other combustible material. Please tell a little more about the construction and composition of the burning mix, which should give you the purple color. With the information you supply no useful answer can be given.

What do you mean with desensitized ammonium nitrate? In fertilizers it is mixed with some form of chalk (a mix of calcium carbonate and magnesium carbonate). It can be purified very easily, by dissolving it in water, letting the solid settle, decanting the clear liquid and slowly evaporating to dryness (at most 90 C, otherwise it may decompose violently, so be careful). Ammonium nitrate, however, certainly is not the best chemical for pyro-purposes. It is very hygroscopic and compositions made with it are not very stable, due to this. It is hard to make a nice dry composition.

The dry chemicals do not react, there is no way that the sulfite (or metabisulfite) can be oxidized by iodine. In the presence of water, a reaction can occur. This is a very common and typical high school redox reaction: SO3(2-) + I2 + H2O --> SO4(2-) + 2H(+) + 2I(-) A solution of sodium sulfite in water will become acidic in the presence of iodine. When (meta)bisulfite is oxidized by iodine, a very similar reaction occurs, the only difference is that things are even more acidic: S2O5(2-) + H2O <--->>> 2HSO3(-) HSO3(-) + I2 + H2O ---> SO4(2-) + 3H(+) + 2I(-) ======================================= What is not known widely, but which is visible very well, is that excess sulphur dioxide reacts with iodide ion, to form a deep yellow complex. So, what high school text books teach is that sulfite and sulphur dioxide in the presence of water react with iodine to form iodide, sulfate ion and acid. This is not surprising. What high school text books do not teach is that with excess sulphur dioxide, the liquid becomes deep yellow, and a complex is formed. This complex can be written as [i.nSO2](-), with n equal to 1, 2, 3 or 4. For the interested one, try it. Take some KI and dissolve that in some acid (e.g. dilute HCl or dilute H2SO4). Take some Na2SO3 or Na2S2O5 and dissolve that in some acid as well. Now you have two colorless solutions, one having a smell of SO2. Now mix the two solutions. You will obtain a deep yellow liquid, with a smell of SO2, and in solution the iodide/sulphur dioxide complex.

I would call inorganic ionic bromides only marginally toxic (provided the cation is not toxic), but of course you should not eat them and also the smoke should not be inhaled. As I wrote before, even chemicals, which are not listed as very toxic, must be treated carefully, but I see this in the same line as other household items, which should not be inhaled, nor eaten. Bromides like NH4Br, KBr and NaBr are not more dangerous/toxic than e.g. KNO3 fertilizer, soaps, common household solvents and so on.

I expect that a better result is obtained with NH4NO3 instead of KNO3. This results in less solid lumps, it liquefies more easily.

Of course people can experiment with this and try to reach the same result with other chems, but it also is their responsibility to do those things in a safe way. SFN cannot take any responsibility for accidents, and if people do not feel confident about their abilities to perform this kind of experiments in a safe way then they either should not do it at all, or first ask information from people who are more experienced.

Also best wishes from me. For all those guys (and girls) playing with fireworks keep things safe and I hope to meet all of you next year, with 10 fingers again! But most of all, I wish you all a very succesful and happy 2007!