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Why does burning Mg explode when...


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#1 DandyGurl

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Posted 17 November 2004 - 05:25 AM

you pour water on burning Mg, does it take the O from the H2O and the burn the H2 with the atmosphere? Why does it do this?
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#2 P_Rog

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Posted 17 November 2004 - 05:38 AM

when you pour water on Mg it is not combusting or burning, it is merely reacting chemically with the Mg. It is producing Mg(OH)2 plus H2.
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#3 P_Rog

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Posted 17 November 2004 - 05:41 AM

I do remember this from one of your posts.....

Not to be a bitch but you need to take chem 101...

Any knowledgeable poeple know?



Not to be a bastard but you need to take chem 101...
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#4 Primarygun

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Posted 17 November 2004 - 09:06 AM

What's chem 101?
I'd think the burning magnesium would give a magnesium oxide.
Pouring water onto it, it will break down into ions and the pure magnesium metal is exposed to water.
Magnesium is not very reactive with water. I think it slightly form magnesium hydroxide
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#5 Gilded

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Posted 17 November 2004 - 01:58 PM

Don't they put high temp. fires out with something else than water because the sudden rise in temperature is enough to separate hydrogen and oxygen from H2O by itself?
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#6 HeXeN

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Posted 17 November 2004 - 04:57 PM

Don't they put high temp. fires out with something else than water because the sudden rise in temperature is enough to separate hydrogen and oxygen from H2O by itself?


Yep. Take Thermite for example...the only thing that'll put that out is....whaddaya call it....a haldon dump, i think. You hit it right on the head, it burns so hot it splits the molecule into hydrogen and oxygen, which, as we all know, is a bad combination around flame. Or white hot molten slag. Whichever.
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#7 budullewraagh

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Posted 17 November 2004 - 09:22 PM

when you pour water on burning magnesium, i believe some of the water forms diatomic hydrogen and oxygen, which floats away, then explodes forming water again
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#8 r1dermon

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Posted 17 November 2004 - 10:03 PM

who cares, why would you throw water on burning magnesium, its so damn cool!!!
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#9 jdurg

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Posted 17 November 2004 - 11:36 PM

No, no, no. The high heat does not cause water to spontaneously split into hydrogen and oxygen. If you read any introductory chemistry book, they will go over the alkali and alkaline-earth metals and their reactivity with water. Magnesium metal will react with water, but only when water is in the form of steam. Mg + Steam = Mg(OH)2 + H2. When magnesium is burning, it burns at a temperature higher than the boiling point of water. As a result, the water poured on the burning magnesium immediately vaporizes into steam. The steam then reacts with the hot magnesium metal forming hydrogen gas which then ignites. It's not the high temperature that rips apart the water. It's the magnesium metal which rips apart the water.
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#10 jsatan

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Posted 18 November 2004 - 02:25 AM

No, no, no. The high heat does not cause water to spontaneously split into hydrogen and oxygen. If you read any introductory chemistry book, they will go over the alkali and alkaline-earth metals and their reactivity with water. Magnesium metal will react with water, but only when water is in the form of steam. Mg + Steam = Mg(OH)2 + H2. When magnesium is burning, it burns at a temperature higher than the boiling point of water. As a result, the water poured on the burning magnesium immediately vaporizes into steam. The steam then reacts with the hot magnesium metal forming hydrogen gas which then ignites. It's not the high temperature that rips apart the water. It's the magnesium metal which rips apart the water.


You mean it will only react fast with steam, water will but slow,
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#11 jdurg

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Posted 18 November 2004 - 02:30 AM

Correct. With water, the reaction is painfully slow. At room temperature, no reaction occurs at all. As you heat the water up, you'll slowly see a reaction occur as bubbles of hydrogen gas form on the surface of the magnesium. Once it reaches the boiling point of water, the reaction speeds up tremendously. Another thing that may lead to an explosion is the rapid acceleration in temperature of the water. If you take somewhat cool water and throw it onto a VERY hot surface, it will instantaneously boil off and may do so at an incredibly fast rate. This will lead to a rapid expansion of gas which is basically an explosion. :D
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#12 DandyGurl

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Posted 18 November 2004 - 03:18 AM

Good to know, My chem professor didn't even know when I asked him... So much for taking chem 101...

I think my eyes are permanatly damaged from watching the Mg burn in the dark... So many fun nights...
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#13 Primarygun

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Posted 18 November 2004 - 08:34 AM

chem 101

What's chem 101?
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#14 DandyGurl

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Posted 17 November 2004 - 05:25 AM

you pour water on burning Mg, does it take the O from the H2O and the burn the H2 with the atmosphere? Why does it do this?
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#15 P_Rog

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Posted 17 November 2004 - 05:38 AM

when you pour water on Mg it is not combusting or burning, it is merely reacting chemically with the Mg. It is producing Mg(OH)2 plus H2.
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#16 P_Rog

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Posted 17 November 2004 - 05:41 AM

I do remember this from one of your posts.....

Not to be a bitch but you need to take chem 101...

Any knowledgeable poeple know?



Not to be a bastard but you need to take chem 101...
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#17 Primarygun

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Posted 17 November 2004 - 09:06 AM

What's chem 101?
I'd think the burning magnesium would give a magnesium oxide.
Pouring water onto it, it will break down into ions and the pure magnesium metal is exposed to water.
Magnesium is not very reactive with water. I think it slightly form magnesium hydroxide
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#18 Gilded

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Posted 17 November 2004 - 01:58 PM

Don't they put high temp. fires out with something else than water because the sudden rise in temperature is enough to separate hydrogen and oxygen from H2O by itself?
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#19 HeXeN

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Posted 17 November 2004 - 04:57 PM

Don't they put high temp. fires out with something else than water because the sudden rise in temperature is enough to separate hydrogen and oxygen from H2O by itself?


Yep. Take Thermite for example...the only thing that'll put that out is....whaddaya call it....a haldon dump, i think. You hit it right on the head, it burns so hot it splits the molecule into hydrogen and oxygen, which, as we all know, is a bad combination around flame. Or white hot molten slag. Whichever.
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#20 budullewraagh

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Posted 17 November 2004 - 09:22 PM

when you pour water on burning magnesium, i believe some of the water forms diatomic hydrogen and oxygen, which floats away, then explodes forming water again
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