65 new of 98 responses total.
ZnCl2. It is ionized in solution. Whether a metal reacts with acid to produce hydrogen depends upon its position with respect to hydrogen in the "electromotive servies". Zn is "above" H2; Copper is below. You can force copper to react, though, by changing the conditions. (Sorry for all the typos in #32: an effect of sleep deprivation.)
The way I heard it, you don't get H+ ions. Instead you end up with H3O+ ions, with that loose proton attaching itself to a water molecule.
That is true to various degrees to all ions in solution, since the ions are charged, and water is polar.
You're right Andrew. I reread the chapter in the chem textbook on acids and bases last night. Wouldn't the third bond on H30+ be weaker than the original bonds forming H2), though? What is the charge difference between the ends of a water molecule? I have been trying to figure out the chemical formula of isopropyl alcohol, the stuff sometimes sold as "rubbing alcohol." An alcohol has a formula of the form R-0H, says the textbook, and propane is a 3-carbon hydrocarbon so my guess is this: | | | -C-C-C-OH | | | What does "iso" (Latin for "the same," is all I know) mean in this context? Could you have an alcohol based on an alkene, alkyne or even a benzene ring, rather than an alkane?
Isopropyl has the -OH on the middle carbon, I believe.
Asked my chem teacher about isopropyl alcohol today. He says that the "iso" is sort of a leftover from an older system of naming, and indicates that the molecule is symmetrical. It does indeed have the hydroxyl on the middle carbon, so its proper name is 2-propanol.
..and #37 is 1-propanol (old name: normal or n-propanol). There is no specific *charge* difference between the + and - "ends" of a water molecule. However the water molecule has a dipole moment of 1.87E-18 e.s.u. (you asked...).
You're right, I did :) Textbook descriptions usually say that water has a slight charge on either end, without giving any quantitative description of the actual magnitude of the difference, and I had assumed that it was possible to describe the different distributions of charge in the units of charge itself. I now know better... You know, I might still be wrong about the isopropyl structure. I think it might actually be the case that the middle carbon of the propyl chain has a -C-OH (methanol) group bonded to it; the reasoning behind the name would be that either side of the symmetrical molecule "looks" like a propanol chain. I'm not sure how to name such a compound under IUPAC rules, however; maybe 2-methanol-propane?? | | | -C-C-C- | | | -C- | OH
It is 2-methyl-1-propanol. It is, of course, a *butanol*, but there are so many isomers of butanol that common names are available for only a few. It could also be called 1,1-dimethyl ethanol, but the naming convention calls for the largest simply identifiable radical to be the basis of the name.
Thankyou Rane, Russ, and Andrew (& anyone else whose name I've forgotten) for your answers. Now I will have to think of some more questions. (:
Hmm. I would have guessed that there were only 4 isomers of butanol. I was thinking of two different places for the OH on a straight butane, and two different places for an OH on an isobutane. That doesn't seem like so many to have common names, but maybe it is. The conventional names (I suspect) are: 1-butanol 2-butanol 2-methyl-1-propanol (our friend), and 2-methyl-2-propanol As far as I can tell, none of these 4 have stereoisomers.
Four is "too many" (you know, one, two, three, infinity...). Three have common names; normal (n-), secondary (sec-) and tertiary (t-) butyl alcohols. "Our friend" has no common name. 2-butanol has a stereoisomer since the 2- carbon has four different groups attached. They are d-2-methanol, and l-2-methanol (and of course the racemic mixture).
Ok - I'll accept that four us too many. It sounded like more somehow. Ah - yes I missed the 2-butanol stereoisomer. thx
If dehydration is a Bad Thing, then why does the body excrete more water, the more it takes in? Is there any survival value to this, or is it just a side effect of how the relevant systems work, or what?
Excess water is also a Bad Thing - the body's got to get rid of it.
Ah, okay.
(Lots of things in the body, like nerves and muscles, depend on the ion concentrations of the blood and other fluids being within certain limits. Too much water thins them out, and stuff starts malfunctioning. This is bad, because you don't live too long if your nerves quit on you.)
It is nice, though, that the body goes to the trouble of absorbing extra water and excreting it through a more convenient orifice, rather than just not absorbing it.
Nice why?
Think.
I don't, remember? It's in my handle. :)
Maybe if you'd go to the trouble of absorbing and conveniently excreting your text, you wouldn't have this keyboard diarrhea. ;-)
The human digestive system is open at both ends (mouth and anus). If water went in one end and were not absorbed where would it come out? Orinoco, I think you would enjoy a first-year biology class even if not required. (I am afraid I don't get the joke in 55.)
Russ' remark made the situation clear enough, but thanks anyway keesan...
It was an attempt at humor on response 51.
We are doing genetics in biology at the moment, and so I was wondering: broadly speaking, how is eye color controlled in humans? Is there more than one gene affecting it, more than one allele, or what? We are doing sex-linked genes at the moment. Genetics is fascinating.
Two genes for brown eyes make brown eyes. Two genes for blue eyes make blue eyes. One of each gives you hazel/green/light brown eyes. There are probably several alleles of the brown-eye gene for different amounts of pigment. Don't know if more than one gene is involved. But two blue eyed parents will not produce a brown eyed child, though two brown-eyes can produce blue, as the blue acts recessive.
I'm not sure I understand--two "genes" for brown eyes make brown eyes, or two alleles? In biology class we did one problem where the premise was that there was one gene for eye color and the brown allele was dominant over blue, but Mr. Stanley told me that this was a simplified view. THis hypothesis explains why children of brown-eyed parents can be blue-eyed (if both parents are heterozygous then both can pass down the recessive blue allele) but says nothing about other colors. If there is more than one version of the brown-eyed allele, perhaps there is one "strong" version, fully dominant over blue-eyes, and a "weak" version that is codominant with blue eyes? I could look it up in the big blue tome at school entitled "Mendelian Inheritance in Man" but I suspect any references there would be a bit too technical for me...
My two hazel eyed parents had eight hazel eyed kids.
My two blue-eyed parents had one hazel-eyed kid, and two blue-eyed.
I did a search on 'eye color' with AltaVista. From the first source:
Reliable Answers on Eye Color by the MIT Guy 1
By JJ Brannon
[1]jjbrannon@aol.com
_________________________________________________________________
I was a student of Salvador Luria [Nobel Laureate for Genetics] at MIT.
Two brown-eyed parents can easily have a blue eyed child.
Two completely blue-eyed parents CANNOT have a fully brown-eyed child with
normal eye development except in certain extremely rare circumstances.
The gene for brown/blue eyes is EYCL3 found on Chromosome 15.
The gene for green/blue eyes is EYCL1 found on Chromosome 19.
Brown is the result of melanin deposits in the iris.
Green is the result of [this is debated] lipochrome deposits in the iris.
Blue-grey [and in some albinism, pink] is due to a lack of pigment in the iris
.
The underlayer, called the stroma, reflects light through its cells like
a mirror's silver back. How the pigment is distributed over the iris involves
other genes which produce flecks, rays, rings, partial diffusion or
full diffusion. This inheritance is very complicated and the genes have not
been well identified.
Here are some reliable sources:
http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?227220
http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?227240
http://www.gdb.org/gdb-bin/genera/genera/hgd/ObjectName/2662023?!sub=0
Francis Galton -- Davenport & Davenport -- Bryn & Winge -- Lenz -- Hughs
as discussed in
Human Genetics, Chapter 5, by Reginald Ruggles Gate [1952]
Heredity & Your Life, pp. 286-312, Boyd [1950]
_________________________________________________________________
References
1. mailto:jjbrannon@aol.com
2. http://sln2.fi.edu/tfi/units/life/forums/anatomy/anatomy.html
I was reading about the Apple Airport. It said among other things that the card had a power output of x.x dBm. What is a dBm?
dBm is decibels relative to a milliwatt. 10 milliwatts = +10 dBm. One microwatt = -30 dBm. (Decibels are a logarithmic scale, 10 dB is a factor of ten. One dB is about 1.26.)
i.e., dB = 10*log(P2/P1), where log is base 10 and P2 and P1 are two *powers* that you want to relate. A useful value to remember is 3 dB = close to a power ratio of 2. Some people try to apply dB to voltage or current, but then one has to use dB = 20*log (E2/E1). A related (and commonly used in control theory) terms is the dL - the decilog, which is simply dL = 10*log(X2/X1) are two similar quantities whose ratio you want to express over a large range.
resp:64 Thank you very much Keesan. I will also have a look at those sources.
Ah, now if it had been dBmW, I might have had a chance of figuring it out.
Every profession has its shorthand. dBm is almost certainly in lots of glossaries, so if you'd looked you probably would have found it.
I think it is easier to ask in a conference devoted to such things. Isn't that one of the purposes they serve?
Never said it wasn't, but learning to RTFM is also important.
That requires having the FM.
What happens to oil (alkyd) paint at 30 degrees F, if anything? (Jim left our primer out last night, sitting on a warmed concrete slab, so it may not have gone quite to freezing). Why should you not apply it below 45 degrees?
It doesn't cure rapidly, meanwhile picking up dust (and leaves).
We will not worry then, as the porch warms up rapidly the next morning and these boards are only being painted to act as a vapor barrier, and the plastic on the porch should keep out the dust and leaves.
This was asked in the agora item on candy, retailing and suchlike, but to prevent drift I'll repeat it here: Why are saturated fats solid but unsaturated fats liquid (in general)? My recollection from chem class is that dispersion forces are greater for some reason in straight carbon chains, but I haven't a chemistry book on hand at the moment so I can't check this. On a possibly related note, what happens to butter when one melts it and then allows it to cool again? It changes color and texture, but why, chemically?
Heating butter and cooling it separates a layer of fat (on top) from a layer of other things that dissolve in water and reflect more light. The top layer is what Indians call ghee. It is less likely to burn than the dissolved or suspended matter, and it keeps longer since many microorganisms cannot live in pure fat (they need water and minerals and oxygen, which is blocked by the fat). One method of preserving foods is to pour melted lard or butter or olive oil into the top of the jar of hot food. You can bake the whole thing in the oven for a while to sterilize it.
Unsaturated fats have a lower melting point than saturated fats, in general, for the same carbon number. Yes, it is because the dispersion forces are greater for the saturated fats. A mechanical way to look at it is that the rigidity of the double bonded carbons, which also introduces a "kink" into the fatty acid, interfers with alignment of the molecules and hence with crystallization.
Thank you both. I had heard of ghee but never knew what it really was. Today I looked up hydrocarbons in my chemistry textbook (by someone called Steven Zumdahl, if anyone's interested) but didn't find anything on b.p. and m.p. (I suspect I overlooked it, but as I know the answer in about as much detail as the book would probably give it hardly matters). Thanks again.
You probably didn't overlook it - elementary texts usually don't get into the physics of phase changes except to note they occur, and maybe some values as melting point is used to identify compounds.
The best ghee is said to come from water buffaloes. Water buffaloes are also found in Kosovo, where there are flat wet areas, and a fermented clotted cream is made from the milk. I don't know how the war affected the animals.
As for why saturated fats are generally solid, as opposed to unsaturated ones, it is basically to do with the shape of them. The straight chain alkanes can sit together more closely, resulting in higher Van-Der Vaals forces (instantaneous dipole-induced dipole). There may also be hydrogen bonding effects which are influenced by the double bonds.
Jim asks if ozone can pass through steel, as in refrigerator motors. He heard that hydrogen can pass through steel.
No, ozone cannot pass through steel. Why? There isn't much ozone around. Yes, hydrogen has dissolve in steel - leading to embrittlement.
Most motors are vented to get rid of heat, though, so ozone can escape that way if there's any arcing going on.
The question in #84 betrays two misconceptions:
1.) There's no ozone in a refrigerator's cooling system.
Refrigerator motors are induction motors, which cannot create
ozone. The commutator sparking of brush-type motors makes
ozone; induction motors have no commutators or brushes.
2.) The creation of ozone requires free oxygen. There is
essentially no oxygen in a refrigerator's system.
3.) ozone is very reactive and would have been depleted by reaction first IF any could have been formed.
Jim says 'Yes' that answers his question. Now he wants me to help him set up a database that will be used to record temperature, humidity, and electric meter reading at various times of day, week and month, in DOS. (We are not very far into Linux yet). Or maybe it should be a spreadsheet program. He wants averages and graphs but also to be able to sort and filter. Are there programs that do all this? I suggested finding programs that will import and export text-format files (a pair of programs that you can move data between). He wants to plot and calculate and see how it depends on time of day and presence of housemates. Ideas?
An hollow metal box that weighs 20 pounds is 1 foot on a side and hence has a total (external) volume of 1 cubic foot. It is placed on the bottom of a tank and then welded to the bottom completely around all four bottom edges. The tank is then filled with water to a depth of two feet. With what force is the box pulling upon the floor of the tank because of its bouyancy?
What is more ecologically damaging- using 2 styrofoam cup daily or using water and soap to wash a steel cup twice daily ? Similarly are electric cars more environment friendly, if the electricity used to charge the batteries was generated by say a coal fired power plant ?
A coal fired plant is far less polluting than a gasoline engine because you can clean the fumes at the source with larger and more efficient equipment, also the fumes are generated away from where people are walking around. I think electricity generation is also more efficient than gasoline engines but you do lose something in transmission.
Re #90: No one has been able to solve that problem in over 3.5 years?! Re #91: Sindi is right about electricity. Its generation in a combined cycle gas turbine (CCGT) plant is ca. 60% efficient, nearly twice that of internal combustion engines. Also, it is more environmentally friendly using natural gas.
Cars can also run on natural gas, which is less polluting.
If you can find a natural gas station....
On Hiscock St. near the garbage yard.
Where else? "Natural gas rises as viable fuel, but lack of infrastructure could prevent use in consumer vehicles" "Michigan has 13 compressed NG stations open to the public." http://is.gd/50aKG
I wonder how much acid rain would be welcome if it meant more ozone
You have several choices: