water

[Dr.Nemo]

I am new to chemistry, so this might be a stupid question. Can you manufacture water. If so how? Where could I learn more about it? Would it be hard to make? H20 means 2 hydrogen atoms and one oxygen atom? I would like to learn more? I'm not a very smart doctor!!![o)]

[enigma]

You can burn hydrogen and oxygen. Viola! Water.

Problem is, the hydrogen costs a good deal more than water.

[Chemicalsuperfreak]

You can mix hydrochloric acid and sodium hydroxide. It'd be kind of salty though.

[On Radioactive Waves]

You can also say that you yourself manufacture water during respiration [6)]

[Zargawee]

Producing water is something easy , you can produce it as a basic result , or as a minor one .

When you burn a hydrocarbone , you produce water.
When you add a strong base to an strong acid , you can produce water.
When you burn hydrogen , you produce water.

what you have to , is to isolated water than the other results (except burning hydrogen).

[On Radioactive Waves]

Originally posted by Zargawee

When you burn hydrogen , you produce water.




In oxygen, yes.Could you not also "burn" hydrogen in Fluorine or Chlorine?

[chroot]

Sure. But don't try to bathe with the product.

- Warren

[lavalamp]

Hydrogen is not neccesarily expensive. You could buy a load of concentrated sulphuric acid, then put it in a U-shaped glass container with an electrode at the top of each end, then apply a DC potential difference accross the two. Hydrogen will be attracted to one and Oxygen to the other (at least, their ions will). Then collect the oxygen and hydrogen, stand well back, ignite the hydrogen in the presence of the oxygen, and there's your water.

Of course all of the equipment, acid and electricity are expensive, but that's besides the point.

[russ_watters]

Originally posted by lavalamp
Hydrogen is not neccesarily expensive. You could buy a load of concentrated sulphuric acid, then put it in a U-shaped glass container with an electrode at the top of each end, then apply a DC potential difference accross the two. Hydrogen will be attracted to one and Oxygen to the other (at least, their ions will). Then collect the oxygen and hydrogen, stand well back, ignite the hydrogen in the presence of the oxygen, and there's your water.

Of course all of the equipment, acid and electricity are expensive, but that's besides the point. You don't need sulfuric acid. Just use water (with maybe a little salt in it).

[lavalamp]

I was under the impression that this could not be done with normal water as it dissociated into H+ (well H30+ ions) and OH- ions rather than O2- and H+ ions. I can't really see how a little salt would affect this.
Can you explain to me why it would work then? Plus if you had water to begin with, what would the point be? There's no fun in making water from water.

[russ_watters]

Originally posted by lavalamp
I was under the impression that this could not be done with normal water as it dissociated into H+ (well H30+ ions) and OH- ions rather than O2- and H+ ions. I can't really see how a little salt would affect this. Sending an electric current through water splits it into hydrogen and oxygen by a process called "electrolysis" and is a common way to manufacture hydrogen. I did it in junior high school. The salt is there to add ions to the water to allow the elecricity to flow. Sulfuric acid is mostly water too. Doing electrolysis on it would yield hydrogen, oxygen and more concentrated sulfuric acid.
Plus if you had water to begin with, what would the point be? There's no fun in making water from water. Indeed. You suggested it though. In any case, this is the cycle by which a so called "hydrogen economy" would likely work. The catch of course is that you don't gain anything - used this way its just an energy storage medium. There are several threads on it floating around here.

[Mr. Robin Parsons]

Back in chem lab it was explained that adding a little sulphuric acid to the water, (~5.0%) that you wanted to electrolyse, aided in the function of the electrolysis.

[lavalamp]

I was also told about electrolysis of water, which is what they said it was at the time, but in a later year when I questioned my teacher about it he said that it couldn't be done with water and there had to be sulphuric acid present (or some other acid).

I assume that this is because there are H+ (H30+) ions floating around in a strong acid solution so most of the work has already been done for you.

Incidentally, water does dissociate a little bit at s.t.p. into it's ions and that is why you can electrocute yourself in a bathtub, because water does condunct electricity. It contains 1.00*10^-7 moles / dm^3 of H+ ions at s.t.p. and that is why it has a pH of 7:

-log10 [H+] = 7.00

[Mr. Robin Parsons]

As far as I know, if you remove all of the dissolved mineral salts out of water, (distill/filter it enough) it no longer conducts electricity. It is only conductive because of the salt(s), present in almost all water.

[lavalamp]

You can get de-ionised water, which means that all other ions have been removed from it, but water dissociates all by itself into H30+ and OH- ions.

Have you heard of the constant Kw? It's the ionic product for pure water at s.t.p. and it takes the value, 1*10^14. It's what you get when you multiply together the concentration of H= ions in the water and the concentration of H30+ ions. ie:

[H30+]*[OH-] = 1*10^-7 * 1*10^-7 = 1*10^-14 mol dm^-3

pH is calculated as follows:

-log10([H30+]), as you should know the pH for pure water at s.t.p. is 7, work out:

-log10(1*10^-7) on your calculator and the answer is 7. If you don't have any H30+ or OH- ions in your solution then that solution doesn't have a pH, but you know that water does have a pH therefore it must have either H30+ of OH- ions in it, as it happens, it has both.

[Mr. Robin Parsons]

Isn't de-ionized/demineralized water's ph balanced directly at the center of the ph scale?

[lavalamp]

At standard temperature and pressure, yes. The pH of water is 7 (directly in the middle of the scale). If the temperature increases then more water molecules have the energy to dissociate and therefore the concentration of hydrogen ions in the solution will increase, therefore the pH lowers slightly, down to maybe 6.5.
The water is still neutral at this pH because there are an equal number of H+ and OH- ions, it's just that the pH is not 7 anymore. Therefore a pH of 7 does not necessarily mean that a solution is neutral.

If you work out the concentration of hydrogen ions in a solution of pH 7, you will find that it is 1*10^-7 mol dm^-3 (worked out by doing this: 10^-pH).

[Loren Booda]

At what redshift does water first appear?

What physical properties are peculiar to water?

[lavalamp]

As far as I know, redshift is a phenomonon that occurs when light coming from other galaxies, that are moving away from us, is stretched because they are moving so fast. I don't really see what this has to do with water.

Perculiar properties of water, well when water freezes, it expands. You would expect that it would decrease in size, because after all in solids the atoms/molecules are closer together. This is not the case for water, I think that liquid water at 0 degrees celcius and ice at -4 degrees celcius have the same density. Below -4 the density of ice is greater than that of water, but between -4 and 0 the density of ice is higher.
The reason why water expands when it freezes is because the molecular crystal lattice that forms, holds the water molecules slightly further apart than they would be in a liquid.
The force responsible for the shape of the lattice is called the van der Waahl's force. It is caused by the repulsion of the electon clouds of the oxygen atoms and the repulsion of the nuclei, but the attraction of the electron clouds of the oxygen atoms to other nuclei in other water molecules. These attractive and repulsive forces create an optimum distance for the molecules to be separated for any fixed temperature, (for higher temperatures, the water molecules have slightly higher energies and so the separation distance for higher energy water molecules tends to be larger).
When water molecules aquire enough energy, the van der Waahl's forces are overcome (they don't go away, they are always there), and so the stucture collapses into something that is more dense where the water molecules are free to slide past each other (liquid water). A good analogy for this is like a building, held up with iron girders running through it. But when the forces provided by these girders are overcome, (usually by dynamite), the building just collapses in on itself forming a smaller, more dense, pile of unordered rubble.

I can't think of any other strange properties of water right now, but when, and if, I do I'll post them.

[Loren Booda]

lavalamp,

Cosmologically observed redshift of water spectrum radiated from the depths of the universe could indicate the time water first occurred after the big bang.

Other properties include surface tension and solvability.

[lavalamp]

What is so perculiar about surface tension? As far as I know all liquids have a surface tension. Also, what about solubility?

If you already knew the answers to these questions, why did you ask them?

[Chemicalsuperfreak]

Originally posted by lavalamp
What is so perculiar about surface tension? As far as I know all liquids have a surface tension. Also, what about solubility?

If you already knew the answers to these questions, why did you ask them?

How does water's surface tension compare with other surface tensions? Is water a good or poor solvent? Have you met Socrates?

[lavalamp]

I;m not sure that I understand your post. Can you clarify it a bit for me.

[Loren Booda]

lavalamp,

The redshift question is important to estimate the origin of water-dependent life elsewhere.

I do not know all of the physical properties peculiar to water, except that they are usually related to its hydrogen bond. Water has an uncommon negative meniscus (surface tension curvature); also, water is considered the most universal solvant.

[russ_watters]

Originally posted by Loren Booda
Cosmologically observed redshift of water spectrum radiated from the depths of the universe could indicate the time water first occurred after the big bang. Redshif does not affect whether or not we can detect certain elements. The lines are the same, they just move. So they can still be identified regardless of how much they are redshifted. That is of course how we measure redshift.

[Loren Booda]

Excited water molecules emit and absorb particular wavelengths. By determining the greatest redshift at which these occur, one may ascertain an approximate epoch for the appearence of water in the universe.

Similarly, if I were to find the redshift for an iron spectrum farther away than any other, I could suppose the initial formation of iron occurred at the corresponding cosmological time. The maximum redshift of water in particular might indicate an early time limit for creation of life.

[russ_watters]

I quoted the wrong passage and misread what I was responding to. At what redshift does water first appear? It sounds like you are asking if there is a certain amount of redshift at which you can't discern the lines for water. But I get it now.

[Chemicalsuperfreak]

Originally posted by Loren Booda
Excited water molecules emit and absorb particular wavelengths. By determining the greatest redshift at which these occur, one may ascertain an approximate epoch for the appearence of water in the universe.

Similarly, if I were to find the redshift for an iron spectrum farther away than any other, I could suppose the initial formation of iron occurred at the corresponding cosmological time. The maximum redshift of water in particular might indicate an early time limit for creation of life.

So when was the red shift for water found?

[Loren Booda]

That was my question: have or can we determine the onset of water formation in cosmological history?

[dr.ununquadium]

I didn't read the second page so I don't know if anyone already said this but no you cannot manufacture water because you need a catalyst to help the mixture change from H2 + O to H2O, and the catalyst may not allow for the production of pure water. Anyway distilling salt water is the best.

[Chemicalsuperfreak]

Originally posted by dr.ununquadium
I didn't read the second page so I don't know if anyone already said this but no you cannot manufacture water because you need a catalyst to help the mixture change from H2 + O to H2O, and the catalyst may not allow for the production of pure water. Anyway distilling salt water is the best.

Actually, all you need is a source of ignition. Actually, if you've got the time, all you need is hydrogen and oxygen.

[dr.ununquadium]

although to speed up the process of combining those 2 elements you do use a catalyst, right.

[Chemicalsuperfreak]

Originally posted by dr.ununquadium
although to speed up the process of combining those 2 elements you do use a catalyst, right.

Actually the reaction can go quite fast without a catalyst. As the flaming ghost of Baron Von Hindenburg can attest.

Not the blimp guy, of course, he was dead before the blimp ever flew; but Baron Julius Von Hindenburg, who died in an unfortunate leiderhosen incident.

[Loren Booda]

The difference being that the gas of Julius was methane, having had a bit too much sauerkraut for his britches before an evening smoke.

[FZ+]

I was thinking the enormous airship Hindenberg...

If you are going to use a catalyst, the chances are you want to use it to slow the reaction down, so you don't blow up a couple of city blocks.

[dr.ununquadium]

I didn't know that the mixture between Hydrogen and Oxygen was flamable, i know hydrogen is flamable only with the presence of electricity though.

[Chemicalsuperfreak]

Originally posted by Loren Booda
The difference being that the gas of Julius was methane, having had a bit too much sauerkraut for his britches before an evening smoke.

Oh, the innanity!

[Chemicalsuperfreak]

Originally posted by dr.ununquadium
I didn't know that the mixture between Hydrogen and Oxygen was flamable, i know hydrogen is flamable only with the presence of electricity though.

Pure hydrogen isn't flammable at all. Hydrogen with oxygen is extremely flammable, explosive if the mix is right. You don't need electricty, any ignition source will do. Google "Hindenburg"

[FZ+]

Hmmm... I thought flammable implies we are talking about "reaction with oxygen"....

[Chemicalsuperfreak]

Originally posted by FZ+
Hmmm... I thought flammable implies we are talking about "reaction with oxygen"....

No, I'm pretty sure flammable just means it will burn and emit flames. There are plenty of things that will burn in the absence of oxygen.

[Jeebus]

Originally posted by Chemicalsuperfreak
No, I'm pretty sure flammable just means it will burn and emit flames. There are plenty of things that will burn in the absence of oxygen.

True but flammability does have limits. Some of those limits apply to vapors. The UFL and LFL define the range of flammable concentrations for a substance in air at atmospheric pressure. The limits of flammability may be used to specify operating, storage, and materials handling procedures for a material. They are particularly useful in specifying ventilation requirements for operations involving flammable liquids and gases, correct?

[russ_watters]

Originally posted by Chemicalsuperfreak
No, I'm pretty sure flammable just means it will burn and emit flames. There are plenty of things that will burn in the absence of oxygen. But hydrogen isn't among them.

When something burns, it has a chemical reaction. Think about what the forumla would look like.

For something like magnesium, I've never actually learned how it burns underwater. I would guess though that it takes oxygen from the water by separating it from the hydrogen.