Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: Tintin_Triton on 01/08/2010 08:26:15
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I know it doesn't. Just wanna know why CO2 doesn't support combustion, though to remind you it does burn readily with burning Mg, Na and K.
So my question is why it doesn't do the same with other elements and/or compounds.
Please explain the Thermodynamics as well as the mechanistic part of the question.
And am expecting a very chemist-type answer.
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I know it doesn't. Just wanna know why CO2 doesn't support combustion, though to remind you it does burn readily with burning Mg, Na and K.
So my question is why it doesn't do the same with other elements and/or compounds.
Please explain the Thermodynamics as well as the mechanistic part of the question.
And am expecting a very chemist-type answer.
Your question relates to a chemical balance not a thermodynamic relation
CO2 is an oxide of carbon, a stable bonding of 1 carbon atom with 2 oxygen atoms
It is already oxidized (2 oxides).
http://www.visionlearning.com/library/module_viewer.php?mid=55
http://www.ausetute.com.au/lewisstr.html
http://www.ausetute.com.au/wriiform.html
You need to look at the atomic characetistics of chemical element
Carbon carries an ion charge of +2
Oxygen carries an ion charge of -4
Adding these two elements together add heat promotes a reaction called oxidation of the carbon atom
The difference between the two is an elementry, two electon charges.
Since this is part of the charateristics of the beasts, by themselves, part of their individual identity, which can not be changed chemically as the single element.
The difference of the charge, we add an two oxygen atoms to the carbon atom to provide the balance of the charge the new formed compound CO2...
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If that is the case then it must not react with burning magnesium.....
as i had already mentioned.
And what are the thermodynamic stats relating to combustion with CO2, if any.
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If that is the case then it must not react with burning magnesium.....
as i had already mentioned.
And what are the thermodynamic stats relating to combustion with CO2, if any.
In this case, Luke, No "if", just "definite".
Categorically speaking.
Combustion related to CO2? CO2 is used to extinguish combustion.
To extinguish a magnesium fire the oxygen supply needs to be completely shut off to the burn.
Covering it with dirt is an inexpensive way.
Using CO2, the flame is so hot the convection currents will lift the gas away bfore it has any affect, air tight conditions is needed in this case or an large abundance of CO2.
What are the thermodynamic stats relating to combustion? Heat and fire
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I'm not sure what Tommya300 is on about, I think he doesn't understand that Mg will burn just fine in pure CO2 to give C and MgO.
The reason that things like coal burn is that the reaction of coal with oxygen is exothermic. The products of combustion (mainly CO2) are more stable than the starting materials.
Magnesium also burns because the reaction of magnesium with oxygen to give MgO is also very exothermic.
This is because the energy released when the Oxide ions and magnesium++ ions come together to form the solid is more than the energy required to turn the oxygen and magnesium into ions in the first place.
If you look at the case of burning carbon the energy released is due to the greater bond energy of CO2 compared to the bond energies of the O2 and the Carbon.
The energy released from burning magnesium is so large that it is "worthwhile" to decompose CO2 to C and O2.
In most cases the energy released on burning isn't great enough to make the overall reaction with CO2 worthwhile.
In effect to get something to burn in CO2 you need to supply the energy needed to split it into C and O2; if you don't get enough energy back by burning that something, then the reaction grinds to a halt.
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I'm not sure what Tommya300 is on about, I think he doesn't understand that Mg will burn just fine in pure CO2 to give C and MgO.
The reason that things like coal burn is that the reaction of coal with oxygen is exothermic. The products of combustion (mainly CO2) are more stable than the starting materials.
Magnesium also burns because the reaction of magnesium with oxygen to give MgO is also very exothermic.
This is because the energy released when the Oxide ions and magnesium++ ions come together to form the solid is more than the energy required to turn the oxygen and magnesium into ions in the first place.
If you look at the case of burning carbon the energy released is due to the greater bond energy of CO2 compared to the bond energies of the O2 and the Carbon.
The energy released from burning magnesium is so large that it is "worthwhile" to decompose CO2 to C and O2.
In most cases the energy released on burning isn't great enough to make the overall reaction with CO2 worthwhile.
In effect to get something to burn in CO2 you need to supply the energy needed to split it into C and O2; if you don't get enough energy back by burning that something, then the reaction grinds to a halt.
Glad your here, your right there, Thanks BC, I never knew why CO2 extinguishers were not affective on a Mag fire.
You certainly changed that... I should of not diverted from metalic oxides
2Mg + CO2 __Δ__> 2MgO + C
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Oh oH oH
I see. So it is that ol' stable product business. Hmmm.... great then.
Thanks BC
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I have the same questions and would like any info any of you can supply.