Wikipedia:Reference desk/Archives/Science/2013 December 19

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December 19

Equivalents in Chemistry (in the Winkler Determination specifically)

Greetings Wikipedia Science Reference Desk...

I am studying some material about water treatment when I came across a chapter on the concept of equivalency. I have a BS in chemistry, but I am not used to this concept, to be honest...the concept of equivalents/normal concentrations was not a thing I used often, or really at all past general chemistry. In any case, we have the following reaction:

2I₂ + 4Na₂S₂O₃ ---> 4NaI + 2Na₂S₄O₆

the material I'm reading says that "one mole of thiosulfate is equivalent to one mole of elemental iodine." I am unsure how this is true...2 moles of elemental iodine react with 4 moles of sodium thiosulfate, but here we have "is equivalent to," and the nuance is making the difference. I tried writing the reaction as a redox pair (1 mole iodine plus 2 moles "electron" yields 2 moles iodide, and then 2 moles thiosulfate yields one mole tetrathionate and 2 moles "electron") but with the quantities used here, I divide the molar quantities here by 4 (what the book has been calling "the equivalent number," i.e. the number of "electrons transferred") but I still get that one equivalent of sodium thiosulfate equals only one-half equivalent of elemental iodine. What am I missing? Thanks so much for the help.
PS I can't find too much helpful material for studying this concept online past incredibly facile problems involving mono-, di-, and triprotic acids. An good resources out there? Aquaman590 (talk) 06:30, 19 December 2013 (UTC)

I believe here you need to work from "reaction moles" and not moles of the individual reactants here. The iodine half reaction is:

I₂ + 2 e^- --> 2 I^-

And the thiosulfate half reaction is:

2 S₂O₃^-2 --> S₄O₆^-2 + 2 e^-

Since the two half reactions involve the same number of electrons, they are equivalent to each other. Even in chemistry, language can be imprecise, and from my best guess, that's what they are using the word "equivalent" here to mean. The term Equivalent (chemistry) is really an electrochemical term that refers to how much the charge of a moiety changes in a chemical reaction. Since both half reactions involve the same change of charge (2) then both half reactions are equivalent. --Jayron32 08:23, 19 December 2013 (UTC)

That seems to be pretty much the same way OP approached the balancing and interpretation of the terminology. And it exactly illustrates that there are "2" moles of thiosulfate, which is the confusing aspect. DMacks (talk) 15:52, 19 December 2013 (UTC)

I agree, which is why I brought up the problem with imprecise language... Which is what I think is happening here. --Jayron32 17:35, 19 December 2013 (UTC)

It is confusing. Clearly 1 I2 and 2S2O3 go into the reaction: 1 for 2, and if you want to measure something you'll need that ratio. Maybe "moles of elemental iodine" means moles of the atom I rather than moles of I2 molecule? Maybe one Na2S2O3 is counted as "receiving" the S2O3 and not as "equivalent"?? But maybe the author just fouled up ... it happens ... Wnt (talk) 18:13, 19 December 2013 (UTC)

1 mole of the element Iodine weighs about 126.9g

1 mole of the the element Sulfur weighs about 32g (not 256g)Investigative Reports (talk) 23:49, 19 December 2013 (UTC)

Definitely a mole of the element is one mole of atoms per mole. Definitely a mole of atomic iodine (not paired) is one mole of atoms per mole. But as our article says, elemental iodine vapor is purple because of transitions between molecular orbitals (in the diatomic molecule); they match other sources on this. I think it's pretty clear that there are multiple allotropes of elemental sulfur, etc. So the usage, while quite close to correct, seems erroneous to me, or at least isn't unambiguous. Wnt (talk) 01:52, 20 December 2013 (UTC)

The whole concept of equivalency in the technical sense (not a general "equality" definition) is in play here, because this was contained in a section about equivalent weights and the like. The idea of "elemental iodine" being just an I atom seems to fit the description, but if this is what the author intended, I have some series qualms with his nomenclature...here are some further context clues to see if we can figure this out further. The whole reaction scheme:

2MnSO₄ + 4KOH --> 2Mn(OH)₂ + 2K₂SO₄
2Mn(OH)₂ + O₂ --> 2MnO(OH)₂
2MnO(OH)₂+ 4KI + 4H₂SO₄ --> 2I₂ + 2MnSO₄ + 2K₂SO₄ + 6H₂O
2I₂ + 4Na₂S₂O₃ ---> 4NaI + 2Na₂S₄O₆

In addition to the quip about the iodine-thiosulfate equivalency, it also states that "The number of moles elemental iodine is equivalent to half the moles of of manganese oxide hydroxide [2MnO(OH)₂] in the second and third equations." (Uh, not really...the stoichiometric coefficients are equal!) Then with some further reasoning (about the moles of oxygen being equivalent to half the moles of the magnesium oxide hydroxide...finally something that looks correct) it concludes that the equivalent weight of oxygen is one-fourth of that of elemental iodine or sodium thiosulfate...that number works out if you trash their reasoning and just find the equivalencies (one-half equivalent iodine per sodium thiosulfate in the last eqn, one-to-one iodine-to-magnesium-oxide-hydroxide in the third eqn, and then the half-oxygen-to-1-magensium-oxide-hydroxide) by our ways of reasoning. Leads me to believe there's an error. What do you all think? Thanks for all the help, I appreciate it immensely.Aquaman590 (talk) 07:24, 20 December 2013 (UTC)

How much pseudoephedrine is sold every year?

I'm reading a story about how the big drug companies are trying to keep pseudoephedrine an over-the-counter drug and not require a prescription. So I'm wondering how much of the stuff is being used as a cold rememdy, and how much is getting diverted to methamphetamine production. — Preceding unsigned comment added by 50.43.12.61 (talk) 06:38, 19 December 2013 (UTC)

In 2010 a total amount of 148,934 kg was sold in the US. Source. I assume most OTC pills contain 60 mg, so multiply it by 16667 for the number of tablets it would represent. The actual amount will be less since pseudoephedrine is also used in other preparations, some of them not OTC. Don't know how much of it is used for making meth.

Don't have any figures for Europe, most decongestants sold here contain phenylephrine; in Belgium only one (generic) formulation of 60 mg pseudoephedrine HCl is available since Janssen-Cilag took Rinomar off the market last year. Probably not a significant source for meth manufacture, although the absence of problematic fillers (like polyvidone) in the pills available would make them easier to extract than American equivalents. Ssscienccce (talk) 15:31, 19 December 2013 (UTC)

Pseudo-ephedrine is an effective decongestant. Personally, I'd prefer the cheaper OTC version rather than the prescription. The only reason to restrict is the "War on Drugs" which only makes it more difficult for legitimate patients to acquire it. --DHeyward (talk) 03:10, 20 December 2013 (UTC)

Make sure you get the stats for Mexico. The whole point of banning PE was to put the cartels in charge of distributing meth. Wnt (talk) 04:00, 20 December 2013 (UTC)

But are you sure most of the pseudo-ephedrine is sold in Mexico? Here in NZ, AFAIK most of the pseudo-ephedrine used in the manufacture of 'P' (meth) is actually illegally imported from China and this is even before it was made prescription only. [1] [2] (Although I'm not sure if it was the case before it was made a lot more difficult to get.) These sources [3] [4] [5] [6] suggest it may be the same in Mexico and possibly the US, although I'm not sure if they are all referring to illegal importantion or importantion outside normal pharmacist channels (i.e. importations for the purpose of manufacture which likely wouldn't have been recorded internally as sold) if this there weren't restrictions at the time. Nil Einne (talk) 05:46, 20 December 2013 (UTC)

No space travel conspiracy

I don't know if this is exactly the right place to put this, but a couple of weeks ago I had an argument with someone who was claiming we've never been into space, satellites are fast moving planes, and that all international communication that would require satellite communication actually use over the horizon radio. I've been trying to find what this conspiracy theory would be called, because I want to read some more of their arguments for curisoties sake. I don't believe what they say of course, I just want to know more. Does anyone know what this conspiracy theory is called, and do we have an article on it? 81.138.15.171 (talk) 13:50, 19 December 2013 (UTC)

Don't waste your time. This person is an idiot. Seriously, there is many, many things which prove man's use of space. The person is not worth arguing with. 217.158.236.14 (talk) 14:06, 19 December 2013 (UTC)

I would disagree very slightly with 217.158.236.14. I have found that many of these people are not idiots – but they are sad. One of the few ways they get pleasure is finding an idiot that they can manipulate into arguments, on beliefs that they don't themselves hold (did you get that last bit – many don't believe it themselves). Of course, we all (even the late, great, Albert Einstein) hold some beliefs that are not substantiated by proof nor firm evidence. The art is to differentiate between those that are just unlearned (but are willing to listen to another view point) and those that are leading you down the garden path were there dwell fairies. Should you get to that to the bottom of that path and don't see those fairies yourself. They can then pull out their Ace card. “If I can see them and you can't, then that proves I am a superior being.” It is a psychological trick that has been played out, down through the generations. So where I do agree with 217.158.236.14. Is that if they fall into the former kind, then converse but if they they are not open to looking at things from another view – just stay clear of them. That fact that you bit on their bait puts in their focus for any of their other game-plays. By trying to understand them (e.g. what is the conspiracy called) they are also manipulating you into wasting more of your time. --Aspro (talk) 17:58, 19 December 2013 (UTC)

You would be far better off reading the old classic on beliefs titled the The Golden Bough. [7]. An excellent book for teenagers to read, because after reading it cover to cover (three times) they can see through most of the baloney.--Aspro (talk) 18:17, 19 December 2013 (UTC)

Obligatory xkcd link [8]. Equisetum (talk | contributions) 12:00, 20 December 2013 (UTC)

These views are held (obviously) by the Flat Earth Society (see, for example, this thread from their forum), but I've not (as yet) been able to find any references to them being held by persons who believe the Earth is round. Tevildo (talk) 14:13, 19 December 2013 (UTC)

There is no conspiracy theory that quite fits that description at List of conspiracy theories#Space, although it sounds like kind of a more extreme version of the moon landing conspiracy theories. Red Act (talk) 14:15, 19 December 2013 (UTC)

There is a even better conspiracy. We are all brains in vats. It's impossible to disproof. Or we are all in The Matrix. 220.239.51.150 (talk) 15:36, 19 December 2013 (UTC)

The tin foil hat, national ultra top secret (NUTS) conspiracy theory. Clarityfiend (talk) 17:44, 19 December 2013 (UTC)

You could try reading this. Of course Buzz Aldrin had his own way of dealing with idiots For the background on that see: Astronauts Gone Wild . Richerman (talk) 18:30, 19 December 2013 (UTC)

Swearing on the Bible is such an absurd contradiction. And you know, they were lying. The astronauts never walked on the Moon. They walked on their space boots which were themselves held up by the Moon, but their feet indubitably rested on some Space Age polymer (by definition!) which came from the Earth and returned back to it again. Wnt (talk) 04:08, 20 December 2013 (UTC)

• The person may not be an idiot, but I agree with IP217 here. Argument requires shared premises and the ability to reason. Claiming, for example, that satellites are fast planes is absurd. Low orbit sattelites circle the earth every 90 minutes. One can watch their transit. No airplane flies 16,000 mph, and assuming secret planes that do so, rather than real satellites, is absurd. Likewise, no conspiracy the size of which this joke presumes has ever lasted without people revealing it. Even lies known to two people are just about impossible to maintain. For an interesting argument on when it is not a rational person's responsibility to argue with another person or continue the assumption of good faith, see Objective Communication by Leonard Peikoff. μηδείς (talk) 19:15, 19 December 2013 (UTC)

Sometimes a person might want to play devil's advocate in a tongue-in-cheek "argument" with somebody just to gain insight into that person's thinking process, cognitive ability and education (etc). ~Eric F: 71.20.250.51 (talk) 20:21, 19 December 2013 (UTC)

Are you claiming to be IP 81's interlocutor? μηδείς (talk) 22:12, 19 December 2013 (UTC)

Perhaps; depends. ~E:71.20.250.51 (talk) 22:44, 19 December 2013 (UTC)

Just by looking, could you tell the difference between an airplane flying 600 MPH at 20,000 feet (4 miles) from a satellite traveling 16,000 MPH at an altitude of 100 miles? I think they would both appear to be dots moving at the same apparent speed. — Preceding unsigned comment added by 50.43.12.61 (talk) 05:25, 20 December 2013 (UTC)

Two people in different locations, communicating with with telephones, could tell using parallax. You could see if the object flies below or above the highest clouds. Or get on a plane, fly to 20,000 feet, and see if the object is still well above you (and while you are at it, do the parallax measurement again with a buddy on the ground). If you are willing to widen the definition of "looking", a radar could measure distance and a doppler radar gives you velocity. To observe where even higher-flying satellites are, travel around your country and see where peoples' TV satellite antennas are pointed - again parallax will tell you whether they are pointed at a nearby or a geostationary point. 88.112.50.121 (talk) 08:35, 20 December 2013 (UTC)

Conspiracists never let logic get in the way of their story. ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:56, 20 December 2013 (UTC)

Are you asking about reality, or the conspiracy theorist's world? For the former, the answer is yes, and very easily. I'm an amateur astronomer who sees satellites and airplanes on a regular basis. A plane usually has colored lights that blink at regular intervals, and can be seen at any time. A satellite appears white, has uniform brightness throughout most of its trajectory, can only be seen around sunrise and sunset, and may disappear as it moves into Earth's shadow. --Bowlhover (talk) 19:59, 20 December 2013 (UTC)

Well presumably we're to believe that these planes don't use standard lights. They're specifically designed to perpetuate the Space program Hoax. APL (talk) 00:29, 21 December 2013 (UTC)

In which case there are thousands of people involved in the hoax, none of whom talks, and for some very strange non-money making motive. μηδείς (talk) 17:35, 21 December 2013 (UTC)

It's useful to go back to the source, i.e. Sputnik. It was the object of intense interest in the U.S. for obvious reasons, and so naturally people took every opportunity to argue whether it was definitely in orbit or not, and tracked it by radio and telescope, not just in a few secret government military tracking facilities someplace but across the country. Teams of 150 different observers looked for it, making for more than a little parallax. While conspiracy theories can seem pathological, it never hurts to understand just when and how people became convinced of things we take for granted now. Wnt (talk) 23:53, 20 December 2013 (UTC)

Apollo Hoax believers are common enough, but I agree with Tivilo, I've not heard this extreme of a variant, except from Flat-Earthers. If you're interested in learning more about their wacky beliefs check out their old newsletters from the 70s. (about halfway down that page.) It's quite a trip. APL (talk) 00:29, 21 December 2013 (UTC)

There are some religious geocentrists out there[9]. 88.112.50.121 (talk) 19:33, 21 December 2013 (UTC)

Clocks (not computer or ipods) jumping ahead

Recently (in the past week) some of the clocks in my German town have jumped ahead about 8 minutes. Computer and ipod clocks were not affected but my 3 kitchen/living room clocks and my nightside table clocks were all affected. Also, my Canadian neighbours clocks were affected (I am Canadian). Is there any explanation for this?

The clocks are digital and normal or whatever you call the ones with gears :p — Preceding unsigned comment added by ClockProblem222 (talk • contribs) 21:40, 19 December 2013 (UTC)

[Banned user]

Some clocks receive a radio signal and synchronize themselves to the radio signal. There could have been a fault in the signal.

Some clocks use the power line frequency to control the frequency of the clock. The power in your area could have been running at a higher or lower frequency than normal for a while. Jc3s5h (talk) 01:15, 20 December 2013 (UTC)

Synchronous electric clocks are rare these days. We need to know more about the type of clocks referred to.--Shantavira|^{feed me} 10:22, 20 December 2013 (UTC)

If this is only happening to you and the neighbours whom you know to be human, while the odd blond people are not affected, you might or might not want to read The Midwich Cuckoos, or watch Village of the Damned (1960 film) or Village of the Damned (1995 film). μηδείς (talk) 03:03, 20 December 2013 (UTC)

Medeis (for I assume it is you), your signature is missing. Tevildo (talk) 02:59, 20 December 2013 (UTC)

It was the blonde alien kids who effed with the signature, not me.