2017年1月10日 · $\ce O$ is a free oxygen atom and $\ce{O2}$ is two oxygen atoms chemically bound to form an oxygen molecule. There is no common analogy for $\ce C$, but $\ce{N2}$ is called nitrogen, $\ce{H2}$ is hydrogen and $\ce{Cl2}$ is chlorine, each having the same name as that of their constituent elements.

2018年11月25日 · Likewise $\ce{O2}$ is as much oxygen as atomic oxygen is. The only complication is that what we habitually think of as oxygen is oxygen as a gas comprised of $\ce{O2}$ molecules. Like Humpty Dumpty in Alice in Wonderland, "a word means what [we] choose it to mean" and often we have to add modifiers or alternate terms to avoid ambiguity.

$\\ce{O2}$ has a double bond in its normal form. That is $\\ce{O=O}$. There are no unpaired electrons in this case are there since there are 2 lone pairs on each oxygen. However 1 resonance structure

2018年2月16日 · Oxygen (O2) generally exists as diradicals i.e. each oxygen bonded to each other through single bonds and the remaining two electrons remains on each oxygen atoms as radicals. So this structural feature makes oxygen act as a strong oxidizing agent.

2017年5月30日 · $\begingroup$ The 2 O represents two separate oxygen atoms, ( not connected to one another so free to move around and react independently ), the $\ce{O2}$ is molecular oxygen. $\endgroup$ – porphyrin

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The reaction as you state it is correct only if there will react only one molecule of oxygen. But the reaction describes burning of methane which is supposed to be in the presence of excess of oxygen.

It's there in every high-school textbook: $\ce{O2}$ is the supporter of combustion. Without $\ce{O2}$ combustion cannot take place. Why? And why only $\ce{O2}$? Why not some other element? And, what happens when a combustible gas burns in air? Say $\ce{H2}$?

2012年8月8日 · $\begingroup$ @GregE. generating oxygen is a separate concern from CO2 removal (i.e. wouter dorgelo's 'providing astronauts with fresh oxygen' ... stated in the context of CO2 conversion to C and O2). Yes, you can generate O2 via electrolysis, but it is the concentration of CO2 and its build-up that creates a hazard for humans.

$$\text{combustible stuff} \ce{+ O2 -> } \text{various oxides} + \text{heat}$$ Note that nitrous oxide ($\ce{N2O}$) is also a supporter of combustion, which means that you can use it to carry out a combustion reaction without oxygen--but this is only because $\ce{N2O}$ generates oxygen itself.