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Help ! (about Nernst equation)
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ketjow
science forum beginner


Joined: 07 Jun 2005
Posts: 6

PostPosted: Wed Jun 08, 2005 7:56 pm    Post subject: Re: easy way to obtaian C6H5-OH Reply with quote

Quote:
3rd step
the electrolysis of HO-C6H4-COONa(aq)--->> C6H5-ONa(aq) + CO2(g)

Could U explain why eletrolysis provides CO2?

And how U checked the gasseous CO2?

Are U sure CO2 doesn't comes from the excess of NaHCO3?


ketjow
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WAYNEL1
science forum beginner


Joined: 04 May 2005
Posts: 25

PostPosted: Fri Jun 17, 2005 1:46 pm    Post subject: Re: Conversion of conductivity to molar concentration Reply with quote

I am trying to run this online Pourbaix charting program
(http://www.crct.polymtl.ca/ephweb.php).
I am using Cu with pure water (well close to 18.3MR or 0.055uS).
According to the last message is seems that for Molality I select
10E-7?

Could anyone help with this?

WayneL
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PostPosted: Sat Jun 18, 2005 6:43 am    Post subject: Re: Conversion of conductivity to molar concentration Reply with quote

You are trying to generate a redox potential versus pH plot for a
specific concentration of a specific metallic ion in solution.

The molarity (concentration) of the ion in the solution is part of the
data you need to provide before the program can makes its prediction.

If you couldn't work this out from the web-site in the first place, you
are probably trying to run before you can walk .....

-------------
Bill Sloman, Nijmegen
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WayneL
science forum beginner


Joined: 03 May 2005
Posts: 33

PostPosted: Sat Jun 18, 2005 3:42 pm    Post subject: Re: Conversion of conductivity to molar concentration Reply with quote

I am conducting a series of test using 80uS water and therefore need to calc
the molarity of it.
Pourbaix diagrams are new addition to my field and I am trying to gain an
understanding of them.
If you could be so kind and shine some light on my dilemma I would be
grateful?

WayneL

<bill.sloman@ieee.org> wrote in message
news:1119084199.387764.30360@o13g2000cwo.googlegroups.com...
Quote:
You are trying to generate a redox potential versus pH plot for a
specific concentration of a specific metallic ion in solution.

The molarity (concentration) of the ion in the solution is part of the
data you need to provide before the program can makes its prediction.

If you couldn't work this out from the web-site in the first place, you
are probably trying to run before you can walk .....

-------------
Bill Sloman, Nijmegen
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Guest






PostPosted: Sat Jun 18, 2005 7:33 pm    Post subject: Re: Conversion of conductivity to molar concentration Reply with quote

Quote:
bill.sloman@ieee.org> wrote in message
news:1119084199.387764.30360@o13g2000cwo.googlegroups.com...
You are trying to generate a redox potential versus pH plot for a
specific concentration of a specific metallic ion in solution.

The molarity (concentration) of the ion in the solution is part of the
data you need to provide before the program can makes its prediction.

If you couldn't work this out from the web-site in the first place, you
are probably trying to run before you can walk .....

WayneL wrote:
Quote:
I am conducting a series of test using 80uS water and therefore need to calc
the molarity of it.
Pourbaix diagrams are new addition to my field and I am trying to gain an
understanding of them.
If you could be so kind and shine some light on my dilemma I would be
grateful?

I stopped being a full-time chemist shortly after I got my Ph.D. in
physical chemistry in Melbourne back in 1970, and Pourbaix diagrams are
new to me too.

Since they appear to related the redox potential of specific metallic
ions in solution to solution pH, it isn't immediately obvious what they
have to do with your question.

The conductivity of your 80uS/cm water is the sum of the conductivities
of the various postive and negative ions in your solution. Because
hydrogen ions are particularly mobile in water, a solution of a dilute
acid will give you a conductivity of 80uS/cm at a lower concentration
than a solution made equally conductive with a dilute salt, or a dilute
alkali.

Strong acids and strong alkalis, that dissociate completely in aqueous
solution, give higher conductivities than equal concentrations of weak
acids and alkalis. Compounds that dissolve without ionising - like
sugar - don't have any effect on the conductivity.

So, what have you put in your solutions to get them to give a
conductivity of 80uS/cm? Until we know that, we can't help you to work
out the corresponding molar concentration of whatever it is.

-------
Bill Sloman, Nijmegen
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Dieter Britz
science forum beginner


Joined: 04 May 2005
Posts: 45

PostPosted: Mon Jun 20, 2005 9:44 am    Post subject: Re: Conversion of conductivity to molar concentration Reply with quote

WAYNEL wrote:
Quote:
Is it just a coincidence that the conductivity of pure water is 0.055
and the inv of the molecular weight is 55?

Yes.

For water of that purity, yes, the molality of both H+ and OH-
would be 1.0E-07. For the less pure water, see the other poster.

--
Dieter Britz, Kemisk Institut, Aarhus Universitet, Danmark.
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WAYNEL1
science forum beginner


Joined: 04 May 2005
Posts: 25

PostPosted: Tue Jun 21, 2005 7:53 am    Post subject: Re: Conversion of conductivity to molar concentration Reply with quote

The water's conductivity started off at 0.055uS and over a period of
several weeks it has changed to 80uS and stayed at that for a few
weeks.
So I guess the water has picked up CO2 from the atmosphere, among other
things.
Would this 80uS be applicable to the Pourbaix diagram or is it just the
molarity of say Cu ion disolved into the water solution?


WayneL
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Dieter Britz
science forum beginner


Joined: 04 May 2005
Posts: 45

PostPosted: Wed Jun 22, 2005 5:49 am    Post subject: Re: Conversion of conductivity to molar concentration Reply with quote

WAYNEL wrote:
Quote:
The water's conductivity started off at 0.055uS and over a period of
several weeks it has changed to 80uS and stayed at that for a few
weeks.
So I guess the water has picked up CO2 from the atmosphere, among other
things.
Would this 80uS be applicable to the Pourbaix diagram or is it just the
molarity of say Cu ion disolved into the water solution?

You need to do more than guess at what the conductivity is due to.
Is it CO2? Is it Cu corroding? What is the pH? And how will you
measure the potemntial (of a Cu electrode?) without affecting the
conductivity? You have a few problems there. Are you sure you need
a Pourbaix diagram for this?
--
Dieter Britz, Kemisk Institut, Aarhus Universitet, Danmark.
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WAYNEL1
science forum beginner


Joined: 04 May 2005
Posts: 25

PostPosted: Wed Jun 22, 2005 8:41 am    Post subject: Re: Conversion of conductivity to molar concentration Reply with quote

These are the same questions I have raised and yes you are right mybe
Pourbaix are not for me. But I could use them as an indicator as a map
of what could happen, is this the best way to use the Pourbaix in my
application - as an indicator?

Thanks
WayneL
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Bill Janssen
science forum beginner


Joined: 19 Jul 2005
Posts: 2

PostPosted: Tue Jul 19, 2005 2:53 pm    Post subject: Re: Atmospheric Effect on Dendrite Growth Reply with quote

jacques jedwab wrote:

Quote:
In article <1121760467.786364.301160@o13g2000cwo.googlegroups.com>,
"WAYNEL" <mail@wlawson.com> wrote:



I am trying to calculate if the atmosphere has an affect on the growth
of dendrites, e.g. copper. Eliminating the atmosphere and growing
dendrites in a vacuum may prove to be difficult to run, as the
electrolyte will outgas and thus evaporate.
However, if a test was constructed using Argon or any other inert gas
would one notice an effect?
Consider another test. Rather than using an inert gas, used CO2, could
this effect the growth of a dendrite.
Are there papers on the atmospheric effect on dendrite growths?
Can anyone propose any potential effects the atmosphere may have?
Or is the electrolyte the "dendrite's atmosphere" and this
vehicle may pick up atmospheric contaminates that could produces
various species?


Cheers

WayneL



Most theories of dendrite growth attribute this habit to differential
concentrations of impurities on certain crystal faces, edges, corners,
etc.
But these theories were devised for metal melts.

J.J.


Bell Labs may have published info on dendrites as the telephone

companies had trouble
with dendrites in sealed crystal filters. One of the repair practices
was to put a "megger" on
selected connections and burn the dendrite clear. I seem to remember
Bell Labs publishing
something on the problem. The filter problem (I think) involved Tin. The
problems
I remember were in the 1950's time frame.

Bill K7NOM
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Martin Riddle
science forum beginner


Joined: 20 Jul 2005
Posts: 1

PostPosted: Wed Jul 20, 2005 8:18 pm    Post subject: Re: Atmospheric Effect on Dendrite Growth Reply with quote

Eagle Pitcher (the battery company) had some problems with their sealed batteries and dendrite growth when dischaged and left un-used. I recall a topic on wiskers, but I dont know if its the same chemical process.

Cheers

"Bill Janssen" <billj9@ieee.org> wrote in message news:6eaDe.1577$cg.674@news02.roc.ny...
jacques jedwab wrote:

In article <1121760467.786364.301160@o13g2000cwo.googlegroups.com>,
"WAYNEL" <mail@wlawson.com> wrote:

I am trying to calculate if the atmosphere has an affect on the growth
of dendrites, e.g. copper. Eliminating the atmosphere and growing
dendrites in a vacuum may prove to be difficult to run, as the
electrolyte will outgas and thus evaporate.
However, if a test was constructed using Argon or any other inert gas
would one notice an effect?
Consider another test. Rather than using an inert gas, used CO2, could
this effect the growth of a dendrite.
Are there papers on the atmospheric effect on dendrite growths?
Can anyone propose any potential effects the atmosphere may have?
Or is the electrolyte the "dendrite's atmosphere" and this
vehicle may pick up atmospheric contaminates that could produces
various species?


Cheers

WayneL

Most theories of dendrite growth attribute this habit to differential
concentrations of impurities on certain crystal faces, edges, corners,
etc.
But these theories were devised for metal melts.

J.J.
Bell Labs may have published info on dendrites as the telephone companies had trouble
with dendrites in sealed crystal filters. One of the repair practices was to put a "megger" on
selected connections and burn the dendrite clear. I seem to remember Bell Labs publishing
something on the problem. The filter problem (I think) involved Tin. The problems
I remember were in the 1950's time frame.

Bill K7NOM
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Farooq W
science forum Guru Wannabe


Joined: 25 Mar 2005
Posts: 240

PostPosted: Tue Aug 23, 2005 9:50 am    Post subject: Re: Why the redox titration curve does not start at zero volt? Reply with quote

Borek wrote:
Quote:
On Mon, 22 Aug 2005 18:39:44 +0200, Farooq W <farooq.w@gmail.com> wrote:

Assume that we dip the ORP electrode in a solution that
contains _only _ ferrous ions?

No such animal. If there is water, it can be be reduced or oxidized
(with O2 or H2 evolution):

H2O + e -> OH- + 1/2 H2
H2O -> 2H+ + 1/2 O2 + 2e

You will have some equilibrium between water half reaction and
Fe half reaction. Doesn't matter what kind of Fe ions (II or III)
you put into the solution, always both will be present.

Best,
Borek

Another person explained this observation as follows: Assume we have
_pure_ Fe(II) solution. Whenever we dip a metal in a solution
containing any _other_ metal ions there will still be some finite
potential. Platinum is a metal and you have ferrous ions in the
solution.

This is true experimentally, which I remember doing, i.e. using a iron
nail and aluminum nail, dip them in the same jar containing sodium
chloride solution, connect the external circuit to a galvanometer, and
you see current flowing through the cell.

Conventially, the potentials are introduced using the same metal dipped
in its own ions say, Zn in 1 M Zn(II). If I recall correctly, Nersnt
did say something about metal M dipped in solution of Z ions. He noted
that a potential did develop but that was variable and unpredictable.



Quote:
--
http://www.chembuddy.com - chemical calculators for labs and education
BATE - program for pH calculations
CASC - Concentration and Solution Calculator
pH lectures - guide to hand pH calculation with examples
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rekuci@gmail.com
science forum addict


Joined: 22 Sep 2005
Posts: 98

PostPosted: Fri Sep 30, 2005 1:09 pm    Post subject: Re: Looking for more info on Ceraphite "aka white carbon" tia sal Reply with quote

sal wrote:
Quote:
Greetings All,

I Had a little dream about white carbon so I decided to look it up and what
I found is
that it's called Ceraphite. The problem is all the websites I've found
using google say the same
thing

"Ceraphite is the fourth allotropic form of carbon, also known as white
carbon.
Discovered in 1969, it is one of the softest substances known to man. It is
formed as small
transparent crystals on the edges of planes of graphite when heated to
above ~2550 kelvins at
low pressures under free-vaporization conditions. It is a transparent
birefringent material. Very little
information is currently available about this allotrope [1]."

Does anybody have anymore information about Ceraphite, the uses it might
have, or where I can get more info?

Searching the Science Citation Index brings up exactly 1 result for
'ceraphite' from a 1977 meeting abstract in the obscure journal
'Carbon'. The title of the abstract is "Ceraphite, a hard and
high-strength new carbon material". The abstract is cited all of zero
times. Unless it has another common name, sounds like a case of
wikipedia syndrome to me.
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muha
science forum Guru Wannabe


Joined: 08 May 2005
Posts: 167

PostPosted: Fri Sep 30, 2005 4:01 pm    Post subject: Re: Looking for more info on Ceraphite "aka white carbon" tia sal Reply with quote

There is one more form of carbon that can be perfectly white - although
not very soft. Uncle should have kilos of is in jars somewhere - unless
Devil has eaten him for posting in phys.sci too much


sal wrote:
Quote:
Greetings All,

I Had a little dream about white carbon so I decided to look it up and what
I found is
that it's called Ceraphite. The problem is all the websites I've found
using google say the same
thing

"Ceraphite is the fourth allotropic form of carbon, also known as white
carbon.
Discovered in 1969, it is one of the softest substances known to man. It is
formed as small
transparent crystals on the edges of planes of graphite when heated to
above ~2550 kelvins at
low pressures under free-vaporization conditions. It is a transparent
birefringent material. Very little
information is currently available about this allotrope [1]."

Does anybody have anymore information about Ceraphite, the uses it might
have, or where I can get more info?

Thanks
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rekuci@gmail.com
science forum addict


Joined: 22 Sep 2005
Posts: 98

PostPosted: Sat Oct 01, 2005 1:56 pm    Post subject: Re: Looking for more info on Ceraphite "aka white carbon" tia sal Reply with quote

I responded to this yesterday but for some reason the reply got lost.

Science Citation Index gives exactly one result for 'ceraphite', a
meeting abstract by Japanese scientists from Toshiba Ceramic Co
published in the obscure journal Carbon in 1977. The title is
"Ceraphite, a new hard and high-strength carbon material". Looks like
a case of wikipedia syndrome.
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Google

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