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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Iwillbethebest on March 27, 2009, 09:02:30 PM

Title: what chemical reaction is taking place here? thank you
Post by: Iwillbethebest on March 27, 2009, 09:02:30 PM

hey guys, its my first post here and this is grade 12 chemistry thanks
heres the scenario and the question:

a long strip of zinc metal (on the left hand side of the beaker) and a stick of carbon (on the right hand side of the beaker) is half on a beaker halfway filled with salt water

the top of the zinc metal and the carbon is clipped with an alligator clip (the red wire on the zinc metal and the black wire on the copper metal) and  attached to a voltometer(?)
the reading clearly showed that there is an electric current (weak as it may be) it appeared to be about half a volt in out lab.

even my teacher does not know what is going on here, all he knows about it is that the direction of the electron flow is to the left which means the zinc metal is the negative end making the copper the positive end.

he and i would like to know what chemistry is going on here? what reaction is taking place here (and the equation for it too)? what is the half reduction here (and the equation)? what is the half oxidation here (and the equation)? and maybe the full balanced equation here?

thanks for the help guys appreciate it

Title: Re: what chemical reaction is taking place here? thank you
Post by: Arkcon on March 27, 2009, 11:02:44 PM

If you're really interested in this experiment, you could leave it connected for a while, and look for changes, in the electrodes, and the electrolyte.  If there are tiny bubbles of gas on the electrodes, you could try to collect them, and analyze the gas.  Although I admit, for a weak cell like you've described, this will take a long time.  Is the cell similar to other cells you've learned about?  What happens in those cells?

Title: Re: what chemical reaction is taking place here? thank you
Post by: Iwillbethebest on March 28, 2009, 12:32:10 PM

thanks for the reply
yeah theyre all similarwe still dont get it though
we still dont know the reaction that is taking place here, we dont know the half reduction eqtn as well nor the half oxidation eqtn.

Title: Re: what chemical reaction is taking place here? thank you
Post by: Arkcon on March 28, 2009, 01:17:08 PM

OK, so if you had a cell, of the format:

Cu|Cu2+||Zn2+|Zn

You'd know what was happening, at the zinc electrode, and at the copper electrode.  Now, you've got an NaCl electrolyte and a carbon rod instead.  What red-ox reactions are likely?  Reduction of NaCl to free Na?  In aqueous solution?  Naw.  Oxidation of elemental carbon, to what, carbon tetrachloride?  He-he.  I'm just being silly.  Something happens, but what?  Take some guesses.  Hint:  water doesn't necessarily have to be a spectator this time around.

*[EDIT]*
I made a stupid and confusing typo

Title: Re: what chemical reaction is taking place here? thank you
Post by: Iwillbethebest on March 29, 2009, 06:56:50 PM

thanks you for your continuous help, i really appreciate it
again, just a recap on the details, a strip of zinc metal and a stick of carbon is inside the same beaker where the beaker is filled halfway with salt water.
uhm as i mentioned earlier, my teacher and i (especially myself) dont really know whats going on, so if type a no0b answer pls pardon me.

this is as far as i got:

salt water: H2O + NaCl
cathode:    C
anode:       Zn 

since the direction of the electron flow is from left to right (Zn to C)in this electrolytic cell, we know that the negative end of this cell is Zn, making it the anode and making the C the positive end, cathode. so there must be redox going on in the copper and oxidation in the zinc.

so the anode (zinc) is reacting with the salt water and it is releasing Zn2+ to the salt water solution(?) because it is oxidizing. but idk what moves in to the cathode (carbon) but there has to be something because it is under redox. knowing that is i believe the key to my question. all i know so far is that the carbon is taking in something with electrons bringing it to the other electrode, in this case, zinc where this zinc metal is pushing off Zn2+ to the electrolyte, then back to the carbon taking in something.. and so on, creating an equilibrium.

what do you think? what is the real answer? 

Title: Re: what chemical reaction is taking place here? thank you
Post by: Borek on March 30, 2009, 03:04:10 AM

Quote from: Iwillbethebest on March 29, 2009, 06:56:50 PM

there must be redox going on in the copper

Honestly, I have no idea what the experimental setup is. You are sometimes mentioning copper cathode, sometimes carbon cathode.

Title: Re: what chemical reaction is taking place here? thank you
Post by: Iwillbethebest on March 30, 2009, 10:38:10 PM

ughh, my bad sorry
its carbon, not copper
i seem to get confused bw the two when i type them up
i apologize for the confusion made, it is carbon
thank you

Title: Re: what chemical reaction is taking place here? thank you
Post by: Borek on March 31, 2009, 06:54:14 AM

See my answer in the thread about carbon cathode.

http://www.chemicalforums.com/index.php?topic=32403.0

Title: Re: what chemical reaction is taking place here? thank you
Post by: Iwillbethebest on April 01, 2009, 10:18:08 PM

yeah, thanks i read your answers and it really helped
by any chance would u happen to know the answer to my question?