Sciencemadness Discussion Board

Iron percipitate?

Magius - 9-6-2004 at 17:59

Hey guys, question...

I read somewhere that if Fe+2 ions are added to NaOH that Green Fe(OH)3 percipitate is formed.

Is this true, and could it be accomplished by electrolysis with iron as both the anode and cathode?

This is my first post here, but this place looks like home for students like me who are bored during chem class.

Saerynide - 9-6-2004 at 18:05

I tried the eletrolysis way too. It was one of the first few things Ive tried. It didnt work too great for me though. The Fe was oxidized too much and all I got was icky brown Fe(OH)3 :( I dont think I regulated the voltage properly, as I used 9v :D

Maybe you'll have more luck if you use much less voltage :P

[Edited on 10-6-2004 by Saerynide]

BromicAcid - 9-6-2004 at 18:22


I read somewhere that if Fe+2 ions are added to NaOH that Green Fe(OH)3 percipitate is formed.

Do you mean Fe(OH)2, ferrous hydroxide is easily oxidized but that would be the inital product from the addition of a hydroxide such as NaOH to a Fe2+ solution.

Is this true, and could it be accomplished by electrolysis with iron as both the anode and cathode?

I believe this would be difficult, Fe(OH)2 oxidizes easily and dehydrates easily. But a low enough voltage and division of the cell compartments should facilitate some Fe(OH)2. If you really ment to produce Fe(OH)3 as indicated in your inital post then Saerynide has already confirmed for you that Fe(OH)3 an "icky brown" precipitate does form.

Good luck on future postings and try to make your teacher feel like you're paying attention to them even if you're not. They're happier that way ;)

Magius - 9-6-2004 at 18:29

Well my chem teacher already know's I'm bored, and he acually lets me read his old college text books which is pretty cool.

Sorry to bother you with my n00b questiong, but can some someone explain the difference between amp and volts?

Right now for most of my electrolysis experiments I'm using a car battery charger, which is 50 amps and 12 volts, but its kinda useless if I don't know what it means.

Also, I've read alot about a faraday of electrons (the amount of electrons used to reduce 1 mol of hydrogen?) how does that fit in to electrolysis?


Proteios - 9-6-2004 at 18:36

Originally posted by Magius
I read somewhere that if Fe+2 ions are added to NaOH that Green Fe(OH)3 percipitate is formed.

Where did you read this????... the statement certainly has a letstat vagueness about it!

Quick google seach shows:
FeSO4 + 2 NaOH = Fe(OH)2 + Na2SO4
(white, greenish-white precipitate, easily oxidized to: Fe(OH)3(brown))

google before posting.

BromicAcid - 9-6-2004 at 18:48

Explaining the difference between amps and volts can easily be found elsewhere, the anology that I distinguish them by is, volts are like the diameter of a pipe and amps are the amount of water flowing though at at set speed.

Your car battery charger is ill suited for electrolysis in aqueous solutions, it will boil most anything quickly I bet. Good for molten salts though, look for those crappy plug in battery chargers for like cell phones, raido shack can help but usually the biggest ones are only 1A or so.

A faraday of electrons reduces one mol of a charge. Example, H+ has a +1 charge and takes one faraday to reduce, Ca2+ has a +2 charge and thus takes 2 faraday. Mind you faraday conversions require inital conversion to columbs. Search elsewhere, don't want to spoon feed too much.

Magius - 9-6-2004 at 19:27

Thanks Bromic.

From your post's else where it apears your the man to trust.

Battery chargers?

That seems so weak though...

So then the gas that i see around the anodes and cathode is water being boiled? Not the H2 Cl2 if I do it with aqueous NaCl?

How exactly would I hook stuff up then? Just jury rig it with some wires to the graphite rods for transisters?

Also, are there any other inert electrodes other than graphite and platinum?

Sorry if i'm posting to many questions. I probably could solve some on my own, but my bed calls me, and the soda ran out a while ago.

Saerynide - 9-6-2004 at 19:44

The gas that forms is H2 and Cl2 if youre electrolysing NaCl, but Bromic meant that the huge amount of current going through the cell will heat the solution enough to boil it.

Use powersupplys from computers :D They provide 3.3v, 5v, and 12v :D

To hook it up, just hook it up two graphite rods like you said :)

Marvin - 10-6-2004 at 03:48

Computer PSU's dont tolerate abuse well and with certain types of fail can output lethal voltage/current, the car battery charger is ideal if it really does produce 50 amps. This is higher than any Ive heard of (here they are more like 3 to 5amp). If it looks whimpy you arnt making the solution conductive enough.

Voltage (in volts) is the water pressure.
Current (in amps) is the rate the water is flowing.
A faraday is a meaure of an amount of water that corrisponds to a useful amount of work (in electric tems, 1 mol of charge).
A coulomb is a measure of water that corrisponds to what can be achieved in a short time (in electric terms 1 amp for 1 second).

1 faraday is about 100 000 coulombs, which means you need high currents, or long periods of time to do preperativly useful electrolysis.

The size of the pipe is more the resistance of the peice of wire in this analogy.