altho water is a molecule with covalent bonds, the electrons spend more time around
the oxygen than the hydrogen. That makes the hydrogen positively charged. this is
what makes water a good solvent for polar or charged molecules. Salts like Na+Cl-
solvate in water because there are a lot of negatively charged oxygen molecules and
the Cl- is attracted to the positively charged hydrogen. They dont combine to form
products to any appreciable level while in water. They "associate" without forming
bonds. The difference in solubility of different "salts" is a function of their size
and charge. Lots of large polar molecules wont go into solution or stay in solution
for long. However, the pH of the solution also affects solubility. low pH means an
excess of H+ ions. high pH means an excess of OH- ions. So heat up calcium rich
water and it deposits in the bottom of the coffee pot (comes out of solution), put in
vinegar which is acidic (and heat it) and it dissolves the calcium bringing it back
into solution.
In the case of Na+ and Cl-, the soft alkaline metal sodium (Na) is extremely reactive
and is desperate to give up its one electron in the outer shell so as to achieve a
greater degree of stability. It is extremely difficult to force Na+ to accept an
electron and takes a lot of energy to do so. Unreacted Na is never found naturally
as an element. Cl is an extremely reactive gas. It as 7 electrons in its outer
shell which is highly unstable, and wants a total of 8 in the outer shell which is
extremely stable, like the noble gases. So Cl will rip the electron away from almost
anything to complete the octet in the outer shell. It will not give up that electron
without a great deal of energy put in.
In direct current, the ions do move physically to opposite electrodes, which is why
base metals can be electroplated with copper, gold or silver or other metals.
distilled water is a non-conductor, add salt and it becomes a conductor. agreed
electrons are not normally found "free range", they are normally attached to
molecules on earth. But electrons are shot out of electron guns (like in our TVs)
and even inner orbital electrons are dislodged and shot to produce X-rays (X-ray is
the pure energy given off when the electron is stopped suddenly, like when it hits a
metal plate... think tomato lobbed at brick wall and all the juice flying
everywhere). OTOH, drag your feet across the rug in winter and then reach for the
door knob and all those excess electrons picked up with jump to the metal as a nice
spark .. the electrons flow thru the air. electrons wont flow unless they have
someplace to go.
metal conductors have free moving electrons. and put the + end of the magnet on one
side and the electrons will line up nicely opposite the + charges. they are held
loosely in the outer shells of metal atoms. the other side of the metal plate will
now be + charged. A magnet remains differentially charged all the time. Magnetism
is a force of nature. There are lines of force connecting the negative charges on
one end and the other. Bring iron filings near the magnet and this is readily
apparent.
Pure distilled water in the lab is not the same thing as rain water. yes of course
rain is weakly acidic because it has CO2 dissolved in it.
http://palimpsest.stanford.edu/byorg.../an11-813.html
"For dealing with the peculiarities of distilled water, he recommended putting a
CO2-absorbent canister on the bottle and only keeping it for a limited period of
time.... boiling also gets rid of CO2 absorbed from the air."
The process of distillation involves boiling the water. Now, pH meters work using
conductivity, but due to the fact that distilled water has no ions, it cannot conduct
and taking pH measurements are difficult. There are ways around this, pH paper is
one way.
Na+ and Cl- do not to any appreciable amount form NaOH or HCl, NaOH and HCl are also
soluble in water, they dissociate, they solvate and are stabilized by the ionic
nature of water. When the water evaporates, Na+Cl- forms the salt NaCl, not the
solid NaOH while the HCl stays a liquid. H2O breaks down to OH- and H+ in extremely
insignificant amounts as they are locked into very stable covalent bonds. The
reaction of oxygen and hydrogen to form H2O is explosive with a great deal of energy
given off as the resulting molecule forms a lower energy and stable covalent
molecule. Ingrid


"Gregory Young" wrote:
They do, but ONLY if a charge is applied (electron donor/acceptor). The +
and - ions will combine to form products (soluble if they dissolve), unless
separated by a semipermeable membrane. Nature doesn't allow opposite charges
to exist adjacent to each other, as the - ion will give its electron to the
+ ion. Water is polar, which we were taught in high school chemistry (too
many years ago for some of us), but only weakly so (as its charges are
balanced with H+, 2 of these to one O, with its -2 charge).
Conductors simply pass electrons from one atom to the next. They don't have
to exist as in a charged (ionic) form. They give up electrons freely, vs
insulators that don't. As freely as they give them up however, they take an
electron from the next, to neutralize their then + charge (which they got
following electron donation)

Let's look at a few examples. Pure
(distilled) water contains no dissolved ions. Therefore pure water will
not conduct
electricity. In a simple conductivity experiment as shown below we would
not expect
the light to be on."

Agreed, but don't try it on yourself, as skin salts will allow you to be
electrocuted just as easily as in "regular" water!


Pure distilled water is neutral pH 7.0

I disagree.. you can test this yourself by running a pH check on a sample of
distilled water. It runs about 5.7 or a bit higher. The reason for this is
the presence of dissolved atmospheric CO2, that can not be buffered back to
7 as there are no dissolved buffers/other compunds in pure distilled water
to do that). It is acidic. Try it!

http://www.epa.gov/airmarkt/acidrain...ents/exp1.html

Neutral salts, like NaCl have no effect on pH.

Yes, I said that. There have balanced + and - charges, with products of HCl
, balanced by NaOH


http://chemweb.calpoly.edu/chem/tani...ses/sld039.htm
Ingrid

"Gregory Young" wrote:
When you add NaCl to water, as it dissolves, it doesn't just disassociate
into Na+ and Cl- and stay that way.
Just like H2o - H+ & OH-. In reality they are equilibrium as follows
(we're simplifying and ignoring other cations and anions) NaCl & H2O -
NaOH & HCl
When you add NaCl to H2O, you will be able to measu
H2O, NaCl, HCl, & NaOH, (plus CaCl2, Na2CO3, CaOH2, etc. with water
containing CaCO3, and other products as well with the Mg etc found in
water.)
The only way either a + or - ion can stay dissociated, is if that charge
(ion) is present in excess of the opposite charge. (ie more + charges
than -
available for this discussion)
The easiest example is the hydrogen ion..
Water usually has a neutral pH range (not distilled, which of course is
acidic), unless there is a relative deficit or excess of the H+ ion,
which
reflects upon the composition of the salts, minerals, and other compounds
dissolved in the water..
Excess H+ (resulting from base (buffer) deficit most commonly, as seen in
older water, etc), will result in lower pH, due to excess H+ ions
present.
Reverse is true with base excess and H+ deficit.
The pH of softened water is (should be) no different than non softened
water
as the Na+ and Cl- don't exist as freely charged particles. If they did,
depending on the relative amounts, excess Cl- would combine with H+ from
H2O
forming HCl and drop the pH, vs. excess Na+ combining with OH- from H2O
forming NaOH and raising the pH.
That can be easily tested by measuring the pH before and after an in-line
water softener. It will (should) measure the same.
Impurities in the water can certainly cause ionization of charges, that
is
quite true, depending on their composition. This are certain metals
(electrodes) placed in salt water that can generate a current essentially
forming a weak battery, but they need to be made of electron donating and
electron receiving material, to allow the imbalance of charges that will
allow ionization to occur and current to flow..
Later,
Greg


wrote in message
...
So you are saying that when you put table salt into water the sodium,
Na+
does not
exist as a free ion? that NaCl does not dissolve into Na+ & Cl- ????
Ingrid

"Gregory Young" wrote:
9) sodium exchanged, BTW, binds to chlorides in the water to make
"salt"..
sodium does not exist in the free state (+ charged ion) in water
Happy ponding
Greg