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Topic: Al(s) + FeCl2(aq) --> ???  (Read 14549 times)

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Vespertine

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Al(s) + FeCl2(aq) --> ???
« on: May 05, 2006, 07:32:16 PM »
Hi, I'm new to this community and to these forums. I'm also fairly new to chemistry (only been taking it for about half a year now), but it's something I'm beginning to fall in love with.

Anyways, here is my question. I synthesized FeCl2 by adding HCl to Fe (more specifially, steel wool). However, at the time when I did this, I thought I had created FeCl3. A day later when I added strips of Aluminum to the FeCl2 solution, the aluminum strip "Fizzed" wildly as it dissolved and released a fair amount of a gas in the process (Since there is no gas in Al + FeCl3 --> Fe + AlCl3, the gas produced surprised me, and caused me to do further research into the HCl + Fe Reaction). Anyways, could someone help me out and tell me what exactly Al(s) + FeCl2 produces? I've searched on google for a while now, and have not been able to come up with anything other than the reaction with FeCl3. Thanks in advance.

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Re: Al(s) + FeCl2(aq) --> ???
« Reply #1 on: May 05, 2006, 07:37:20 PM »
Your solution contained not only FeCl2 but also some amount of FeCl3, as iron gets oxidized to Fe(III) by oxygen from air. But that's only a sidenote.

As fro your main question - are you sure Al reacted with FeCl2 solution? Have you used stoichiometric amount of HCl, or excess? What was pH of the solution when you added Al?
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Vespertine

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Re: Al(s) + FeCl2(aq) --> ???
« Reply #2 on: May 05, 2006, 08:34:46 PM »
Yes, the Al indeed did react with the FeCl2 solution, as the Iron in the solution was replaced with Aluminum and an Iron Precipiate (I believe it is iron, it certainly is magnetic) formed. I used an excess amount of HCl, and as for the pH, I am unsure as I did not test it beforehand.  :-\

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Re: Al(s) + FeCl2(aq) --> ???
« Reply #3 on: May 06, 2006, 03:57:29 AM »
You didn't get it. If there was an excess of HCl Al reacted with this excess, not with FeCl2. So what you have seen was simple Al dissolution in acid.
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Vespertine

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Re: Al(s) + FeCl2(aq) --> ???
« Reply #4 on: May 06, 2006, 09:47:38 AM »
Ah, okay... You said before that a certain amount of FeCl2 would be oxidized to FeCl3 by oxygen in the air, and I think that a certain amount of the aluminum replaced the Iron in the iron(III) chloride creating the iron precipitate I see, and the rest reacted with the excess HCl acid. So basically, Aluminum will replace the Fe in FeCl3 but it won't react with the FeCl2? Again, thanks for the help.  ;)

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Re: Al(s) + FeCl2(aq) --> ???
« Reply #5 on: May 06, 2006, 09:57:18 AM »
Not exactly. What is happening is that first Al reduces Fe3+ to Fe2+, then it reacts with excess HCl and finally (if there is any Al left) it reacts with Fe2+.

You have to look at half-reaction potentials to check such things. Note that I have used only standard potentials when describing situation, in reality potentials depend on the ions concentrations, so details may vary.
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Vespertine

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Re: Al(s) + FeCl2(aq) --> ???
« Reply #6 on: May 06, 2006, 10:26:29 AM »
Ah, okay! Thanks for your help, I now fully understand what has happened.  ;D

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