Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: taregg on 06/11/2011 01:44:16
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exsample hydrogen ,carbon and.....
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In the right circumstances most elements will burn.
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In the right circumstances most elements will burn.
You could eliminate the noble gases, although most of them will form unstable compounds in certain situations.
There are a number of halogen oxides. BC might be able to better describe whether the oxygen is the oxidation or reducing agent, or perhaps it depends on the compound.
You can make Gold Oxide, (http://en.wikipedia.org/wiki/Gold%28III%29_oxide) but it is not particularly stable.
Many, or most other materials can undergo a violent oxidation (burning). For example, one thinks of iron oxidation (rusting) as being a slow process, but given the right conditions, steel and iron will burn (the basic principle of oxyacetylene cutting).
Certainly you can also have violent reactions without the presence of oxygen.
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Of all the roughly 100 well-characterized chemical elements, only helium, neon, argon, and bromine have no known reasonably stable oxides at ordinary temperatures. Bromine oxides are known, but are only stable at very low temperatures (< -40°C).
To these four you could add nitrogen, krypton, xenon, platinum, and gold that do not react directly with oxygen to any great extent.
All of the other roughly 90 elements react directly with oxygen gas in the right conditions.
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The question relates to fire. The previous answer is correct regarding oxidation by oxygen with sufficient partial pressure of oxygen and temperature.
As indicated, you won't find gold or platinum burning in air at normal pressures. Gold oxide is unstable. While palladium oxide has a negative heat of formation, it's too small (-85.4 kJ/mol) to sustain fire. Iron(III) oxide has an enthalpy of formation of -824.2 kJ/mol and can sustain fire but only if the heat is not conducted away from the oxidizing surface too quickly. You can burn fine iron wool but not chunks of iron.
The first column of the periodic table contains the alkali metals that all will burn readily once started. Potassium oxide has an enthalpy of formation of -361.5 kJ/mol.
The second column contains the alkaline earth metals. Magnesium, for example, burns with a brilliant flame that is so hot that it emits heavily in the ultraviolet and can damage your eyes if you look directly at it. The heat of formation of magnesium oxide is -601.6 kJ/mol.
As you move across the periodic table, the likelihood of fire decreases. Oxygen diflouride is a gas with a positive heat of formation. Thus, fluorine won't burn in air. Chlorine, bromine, and iodine have the same problem. While you can oxidize some noble gases, they won't burn or even oxidize under ordinary conditions.
In theory, most of the remaining elements (except for oxygen [:)]) can burn. In some cases, bulk amounts will not burn because the heat of combustion is conducted away too fast to continue the burning process.
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"You can burn fine iron wool but not chunks of iron."
http://en.wikipedia.org/wiki/Thermal_lance
"As you move across the periodic table, the likelihood of fire decreases."
Have you seen where sulphur is? What about phosphorus?
I think Caltech must be letting its standards slip.