jdurg

The gray skin is probably a simple oxide coating, as I've seen that happen numerous times with samples of Ga. (Hence why I use the Cu wire to skim off the 'gunk' as it is solidifying).

Guys, guys, guys. You've made some good posts here, but from the nature of the initial question the concepts of stereoselectivity, moles, electronic structure, etc. are probably way over the initial poster's head. Let's try and keep things simple and just introduce him to the basics. Any general chemistry textbook will be good at telling him anything he needs to know. Getting him into complex concepts and ideas too soon will just frustrate him and make things much more difficult down the line. Onemind; the important thing to remember is that chemistry is a building process. Without a solid foundation you'll have a very difficult time moving ahead. Try and set small goals for yourself and take the subject in small doses. If you try and learn it that way, you'll have a much easier time as you get further and further into the subject. Take a look at your general chemistry textbook and try and do as many of the sample questions as you can. Pretty soon you'll be able to answer them without any problems at all. When that happens, move on to the next chapter etc. etc. (And in case you were wondering, the term 'moles' is simply a counting concept. Like a 'dozen', or a 'pair', it's a term used to describe the number of something.)

For the HCl solutions, HCl is a strong acid so whatever the concentration of the HCl is will be the concentration of the H+ ions in the solution. Therefore the pH would be the negative logarithm of the H+ concentration. For the last two questions, you need to look at them as an equillibrium since they are both weak acids/bases. For a weak acid, you have to realize that it's conjugate base (acetate in this case) will want to grab a hydrogen atom from water and form the main acid again. As a result, any solution of the negative ion portion of a weak acid will be basic. Therefore, the equation you need to look at is that of the dissolution of a base. You will also need to look up the Kb of the acetate ion as the Kb is the equillibrium constant of the acetate ion reforming acetic acid. (If you don't have the Kb and you only have the Ka of acetic acid, remember that Ka*Kb = Kw = 1.0E-14). So when you write out your equation, you would write it like this: CH3COO- -> CH3COOH + OH- (This is not a fully balanced equation, but when dealing with acids/bases you just need to write the species which are involved in the reaction. We're not including water on the left hand side simply because there is so much water in the solution that the concentration really doesn't change). So now we can write out our equillibrium expresssion; Kb(acetate) = ([CH3COOH][OH-])/[CH3COO-] Initially, we have no acetic acid and no OH- in solution so their concentrations would be 0. As an example, we'll assume that we have a 1 molar solution of sodium acetate which would give us one mole of acetate ions. If we use an I.C.E. chart (Initial concentration, Change at Equillibrium, and Equillibrium concentration), the I portion would look like this; CH3COOH=0, OH-=0, CH3COO-=1. At equillibrium, the changes would be +x, +x, and -x as every mole of acetate forms one mole of OH- and CH3COOH. Finally, the equillibrium concentrations would be CH3COOH=x, OH-=x, CH3COO-=1-x. With the Kb of acetate being 5.6E-10, you just need to solve for x. Solving for x should give you a value of about 2.4E-5. That is the concentration of the OH- ions in solution. In order to figure out the pH, you need to know that pH+pOH = 14, and pOH = -Log([OH-]). With the numbers we've come up with, this gives a pOH value of about 4.6. 14-4.6 = pH = 9.4. So the pH of a one molar solution of sodium acetate would be 9.4. The same process is used for any salt of a weak acid. If the salt is of a weak base, then you would use the Ka of the conjugate acid and adjust your equillibrium expression accordingly.

It's phonetically prounounced as 'Ba-lone-E'. It's a concoction of various meats and animal products squished into a sausage like form. I personally find it nasty. As for practical jokes with cars, I find this one particularly good. Now mind you, this only works in the winter when the temperatures are far below the freezing point of water and it takes some time to actually work. If someone parks their car where they shouldn't be parking and are gone for the whole day, you take a little squirt bottle with a nozzle and fill it with water. You then take the nozzle and put it in the keyhole of the car and just start squirting water in there. Given enough time, the water will freeze into a solid block of ice INSIDE the keyhole of the car. The jerk who parked where he/she should not have parked will be unable to get his/her key into the hole and will have to somehow melt the ice in order to open up their car door. I did this back in college when some real jerk parked his BMW right in front of our apartment instead of paying the 5 bucks to use the public parking lot. Let's just say that it was really funny watching some idiot in a suit trying to melt the ice using a zippo lighter.

That sterile hospital smell is an odd concoction of ozone, chlorine, nitrogen oxides, organic ethers, etc. etc. from the sterilization/cleaning solutions that are used, the high electrical discharges from the x-ray and other high powered analytical machines, and various other things being used in a hospital.

Yeah, in anhydrous conditions I just can't fathom any type of reaction between SO3 and NH3. I don't think SO3 is a strong enough oxidizing agent to oxidize the ammonia, and ammonia isn't a strong enough reducing agent to reduce the sulfur trioxide. In an aqueous environment, the water can act as an intermediate and cause the SO3 to form sulfuric acid, like you mentioned above, and the sulfuric acid will then be able to react with the ammonia.

If the initial equation was a correct one, the answer would/should be: 3Ca + 2Sc3+ -> 3Ca2+ + 2Sc

The original question is therefore incorrect and you should bring that up to whomever gave you the question. Ca+ simply does not exist in any stable compound used to produce scandium metal. Elemental calcium has a charge of 0 on it. Even though I HATE when teachers/professors give hypothetical equations that are impossible to actually happen, I will help you out here. The first thing to do is see what the oxidation numbers are for each of the species involved. On the reactants side you have Ca+ with an oxidation state of +1 (shudders) and Sc3+ with an oxidation state of +3. On the products side, you have Ca2+ with an oxidation state of +2, and Sc with an oxidation state of 0. So now you have to split the products and reactants into half reactions. We'll start with just scandium. If you remove the Calcium part from the equation, you get "Sc3+ -> Sc". In order to balance the charge, we have to add 3 electrons to the left side of the equation. This gives us "Sc3+ + 3e- -> Sc". The charge is now balanced. (Remember, when balancing equations both the charges and the atoms involved have to be balanced. To keep a charge balanced, just add and subtract electrons). Now we'll look at the calcium. If we remove the Scandium portion, we get "Ca+ -> Ca2+". To balance the charge, we have to add an electron on the right side. This gives us "Ca+ -> Ca2+ + e-". Now we add the two equations together. Sc3+ + 3e- -> Sc Ca+ -> Ca2+ + e-. We need to balance the number of electrons as we have three on the left side and only one on the right. So if we multiply the second equation by 3, we get the following: Sc3+ + 3e- -> Sc 3Ca+ -> 3Ca2+ + 3e- 3Ca+ + Sc3+ -> 3Ca2+ + Sc The electrons cancel each other out and you get the equation seen above.

Doesn't remind me of chlorine at all. It reminds me of the smell of a thunderstorm and the smell of an x-ray machine. (Probably because both of those things result in the production of a good deal of ozone).

Yup. And because of the low temperature of the explosion, you don't have to worry about things in a close proximity catching fire like you would with other explosive compounds. (Things like TNT and trinitroglycerol may ignite flammable materials nearby due to their higher 'detonation' temperature, if that's what it's actually called. Hence why they make such good millitary explosives).

Mmmmm....... Ozone. I completely forgot how much I abhorr that smell! It's that odd smell you find when you're in the X-Ray room of a hospital. Just the slightest hint of Ozone really gives me the creeps as it reminds me of having to go into the back, dark corners of a hospital basement to get x-rays done, and the pain associated with the broken bones that required the x-rays. I always get the heebie-jeebies when I smell ozone due to those memories.

Yeah, but if you're using it for the intended purpose of an explosive (which is to move large amounts of material in a short period of time), any loud brisance or emission of light is a waste of energy.

Hehe. Nope. It's just another one of those chemicals where once you get a small whiff of the stuff, you never forget it. (Just like HCN and Arsine).

Actually, NH4NO3 is one of the best explosive compounds out there. Tons of it are used every year in the construction and mining industry. It is VERY powerful and very insensitive, but incredibly effective at what it does. However, the NH4NO3 does need to be prepared and packaged in a certain way, which I will NOT describe here, in order to become that good explosive composition.

Yeah, I got a whiff of it in one of my analytical labs in college. I forget the exact details of the lab, but we were instructed to keep the small vial inside the fume hood and to not get any of it on our skin. Even though the fume hood was working quite well, if you got close enough to the opening of the hood you could get a tiny whiff of the stuff. It REALLY smells bad. It's a very unique, but very bad odor that's pretty difficult to describe. All I know is that I would not want to be anywhere near a vial of the stuff that isn't inside of a fume hood. It also makes me very thankful that my solid osmium pellets don't oxidize at all unlike their powdered bretheren. (Now that I think about it, I think the lab had to do with fingerprint analysis so it was probably my forensics lab as opposed to my analytical lab).

Bad: Chlorine, putrescine, cadaverine, amyl alcohol, most organic amines, skatole, thioesters, arsine, bromine, osmium tetroxide, hydrogen sulfide, sulfuric acid, acetic acid, sulfur oxides, acetone, ammonia. Good: Hydrogen cyanide, ethyl acetate, benzene, toluene, nitric acid, iodine, methanol, ethanol, diethyl ether, octane, cyanoacrylate, phosphorus oxides, most simple small chain organic esters, perchloric acid (I don't know why, but I like the smell of it as it's a bit 'different' than the bad chlorine smell), xylene.

Zirconium metal burns VERY brightly when ignited. Moreso than Magnesium I believe.

There's also the resistance to the flow of electrons, and any time you have resistance in an electrical system it will generate heat. Water has some resistance to electrical 'flow' so the power wasted when the electrons aren't flowing is translated into heat.

I honestly do not believe that there are any colored gases which are non-toxic. All gases that I know of which have a color are quite toxic and corrosive. (NO2, Cl2, Br2, I2, etc. etc.). Of those gases, only Cl2 can be considered 'green', but if you had enough of it to see the green color, you'd be dead if you were close enough to inhale it.

Am-241 has a half-life of about 432 years. So if one microgram of it was in a smoke detector made in 1573, we'd have half a microgram of it. (And Am wasn't discovered until 1944, so if one gram of it was made way back then, I believe it would have decayed into about 0.93 grams of it today).

I don't believe any special acid is formed. What you get is a strong oxidizer under acidic conditions, and any mixture of strong oxidizer and an acid is a VERY potent substance. Nitric acid is not really a very strong acid, but the nitrate ion in acidic conditions is a very potent oxidizer. As a result, nitric acid can dissolve most anything. Hydrochloric acid is a poor oxidizing agent, but if you mix it with a strong oxidizer (nitric acid or hydrogen peroxide), it becomes a very potent oxidizer. So whenever you mix a strong oxidizing agent like hydrogen peroxide with an acid, you wind up with the oxidizer under acidic conditions which results in a very corrosive and dangerous mixture.

Doesn't matter if it's old or new. Am is used in all smoke alarms and the half-life is so long that even the very first smoke alarm will have Am in it.

Exactly, the precise timing required to get all the subcritical masses fusing at the same time is remarkable. If the timing is off by just a fraction of a second, the bomb basically becomes a dud. In order to go critical, the masses have to come together and form one supercritical mass before the explosive compositions themselves blow the mass apart. This is why you can't get a nuclear bomb to 'go off' even if you hit it with another missile. The explosion that would happen is not the impeccably timed explosion needed to create the supercritical mass. With modern bombs, the circuitry inside the bomb that controls the initiation of the explosion is quite complex. It's also VERY well protected from any type of electrical/EM interference. I mean, the circuitry is in an enclosed area with several kilograms of highly radioactive material. It should definitely be able to withstand EM and any other electrical interference, otherwise the nuclear 'fuel' itself would damage the circuitry.

Very nice. Who would have thought that chemistry would have a practical application to it? (I'm also assuming that the NaOH worked because the oil was freshly spilled. If the oil had time to really soak in, then you'd need to take powdered NaOH and sprinkle it over the stain, add a little water, and make sure that the area is WELL sealed off to prevent people or wildlife from severely injuring themselves. Then you'd have to neutralize the NaOH with some muriatic acid. With a fresh oil stain, the oil will not have seeped in as far and the need for anhydrous NaOH isn't really necessary. Plus, the acidity of the pavement will help neutralize any excess).