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Topic: ZnO and H2 ???  (Read 19278 times)

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Offline n0m0r3l0v3_0k

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ZnO and H2 ???
« on: November 03, 2008, 06:21:23 AM »
I have a question about ZnO and H2, need to consult your opinions. Can ZnO be deoxidated by H2? In my opinion, there is no reaction because H2 isnt strong enough to "steal" the O in ZnO. I already read some book abt this but when I did my test, the correct answer is that H2 can deozidate ZnO. Someone solve me this problem plz. Thanks alot

Offline AWK

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Re: ZnO and H2 ???
« Reply #1 on: November 03, 2008, 06:52:02 AM »
Of course you can reduce ZnO, but in high temperature in which Zn will react with one product of reaction, namely H2O. Metallic zinc is produced by reduction with C instead of H2 .
AWK

Offline Arkcon

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Re: ZnO and H2 ???
« Reply #2 on: November 03, 2008, 09:09:42 AM »
Many metals that resist reduction by carbon can be reduced by heating in a stream of hydrogen, the constant motion pushes gaseous products away.  This is a little dangerous, so if you can reduce with carbon, you do that instead.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline cliverlong

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Re: ZnO and H2 ???
« Reply #3 on: November 03, 2008, 02:56:39 PM »
Of course you can reduce ZnO, but in high temperature in which Zn will react with one product of reaction, namely H2O.
Quote from: AWK
Many metals that resist reduction by carbon can be reduced by heating in a stream of hydrogen, the constant motion pushes gaseous products away.
Sorry, I don't understand why either of those statements are true.

My understanding of the relative reactivity of Zinc, Hydrogen and Carbon is summarised in the following diagram

http://www.gcsescience.com/r1-reactivity-series-metals.htm

From which I understand Carbon can reduce Zinc oxide to zinc because carbon is more "reactive" than zinc

But hydrogen CANNOT reduce Zinc oxide to zinc because hydrogen is much less "reactive" than zinc.

How can changing the reaction conditions such as streaming hydrogen over the oxide have any effect on the reactivity? Why does reacting ZnO with H2 at high temperature have any impact?

Could you explain
Quote
in high temperature in which Zn will react with one product of reaction, namely H2O.
a little more as I don't understand what you have written


Thanks

Offline Arkcon

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Re: ZnO and H2 ???
« Reply #4 on: November 03, 2008, 03:35:46 PM »
Sorry, but web resources for this obscure method of reduction are in short supply.  A quick Google led me to this text book reference:

http://books.google.com/books?id=2PAarkWieIQC&pg=PA373&lpg=PA373&dq=hydrogen+reduction+metal+oxide&source=web&ots=pamg71Cd4A&sig=r4IbmqYU7MVMV153ohuM_2ySRoU&hl=en&sa=X&oi=book_result&resnum=7&ct=result

Which, makes only casual reference to the use of hydrogen as a reductant (scroll down a couple of pages.)  I haven't checked you reference yes, but as I understood it, elemental hydrogen has greater reducing power than elemental carbon.  Kinda follows logically, doesn't it, when you compare the likelihood of finding either element free, right?

This was an old, old, method of reducing a metal oxide.  You put a small porcelain boat containing the metal oxide into a cylindrical glass tube supported on it's side.  You pumped hydrogen through the tube, to drive out air, exhausting the hydrogen far away.  Otherwise the tube is sealed.  You heat the tube under where the boat is.  You get free metal as a result.  Does that sound plausible?  Anyone?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Arkcon

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Re: ZnO and H2 ???
« Reply #5 on: November 03, 2008, 03:43:07 PM »
Oh look, one of the biggest problems faced is not that you can't reduce group II elements with hydrogen, but rather the temperature required vaporizes the metal.

http://findarticles.com/p/articles/mi_qa5348/is_200710/ai_n21301988/pg_1
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline cliverlong

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Re: ZnO and H2 ???
« Reply #6 on: November 04, 2008, 02:29:38 AM »

This was an old, old, method of reducing a metal oxide.  You put a small porcelain boat containing the metal oxide into a cylindrical glass tube supported on it's side.  You pumped hydrogen through the tube, to drive out air, exhausting the hydrogen far away.  Otherwise the tube is sealed.  You heat the tube under where the boat is.  You get free metal as a result.  Does that sound plausible?  Anyone?
Without looking it up - I remember that method being used for copper oxide to copper - which is consistent with the order of reactivity of metals - that is hydrogen is a stronger reducing agent than copper so it will "take" the oxygen from copper oxide.

Interesting thread - has made we think again what "reactivity" actually means.


Clive

Offline chesternham

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Re: ZnO and H2 ???
« Reply #7 on: November 08, 2008, 06:59:38 PM »
As far as i know, H2 can react with ZnO to release water H20 and ZnO changes into Zn,we name this reaction is REDUCTION but the condition is ZnO has to be heated between 500 -600 Celcius because it is strong enough to carry out the reaction except to Gold.                                                                                                                                                                   The equation is : H-H + Zn-O --> H-O-H + Zn (H2 + ZnO -> H2O +Zn)                       
To perform this  reaction u have to be in lab with  lab  equipments !!! No burning H2 outside Unless you wanna die



Remember nothing i imposible in science !!! With the modern tech,we can even use any machine to produce compound .

Offline Borek

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Re: ZnO and H2 ???
« Reply #8 on: November 09, 2008, 05:32:43 AM »
Remember nothing i imposible in science !!! With the modern tech,we can even use any machine to produce compound .

That's not the way it works. If something is thermodynamically impossible, it is impossible. That's what the science tells.
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