wrote in message
...
yes. it does dissolve and stay that way unless the water evaporates. Na+
and Cl-
are free ions in water.
http://basd.k12.wi.us/~kreutz/SolutionChemistry.html
"How do we know that ionic solids dissolve in water and form cations and
anions that
float around separately? One clue comes from conductivity experiments.
Anions and
Cations should act as charge carriers in solution. Therefore a solution
with
dissolved ions should conduct electricity.
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