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Topic: How come there is no combustion?  (Read 2292 times)

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Offline INeedSerotonin

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How come there is no combustion?
« on: September 23, 2019, 01:56:09 PM »
In the following table, there are four reactions of decomposition, and they happen with explosives.



When there is an explosion of 1 mole of each of these explosives, in standard temperature and pressure, the wrong option is that

a) what happens is a combustion;

b) TNT produces solid residue;

c) the inorganic one is the one which produces less gas;

d) the nitrocellulose is the one which produces more gas

How come? If there is an explosion, isn't there a combustion? This doesn't make sense to me. Can someone explain it to me please?

Offline AWK

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Re: How come there is no combustion?
« Reply #1 on: September 23, 2019, 02:44:24 PM »
Compare Wikipedia explanation for combustion and explosion (chemical).
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Offline INeedSerotonin

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Re: How come there is no combustion?
« Reply #2 on: September 23, 2019, 04:14:10 PM »
Thanks, but I still don't see how can an explosion happen in standard temperature and pressure, or how can it happen without a combustion.

Combustion:

Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke.

Explosion:

An explosion is a rapid increase in volume and release of energy in an extreme manner, usually with the generation of high temperatures and the release of gases. The most common artificial explosives are chemical explosives, usually involving a rapid and violent oxidation reaction that produces large amounts of hot gas.

Perhaps the exercise is poorly phrased? Or I just couldn't grasp the concept...

Offline Borek

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Re: How come there is no combustion?
« Reply #3 on: September 23, 2019, 06:26:41 PM »
Name the fuel and the oxidant in a TNT explosion.
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Offline Vidya

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Re: How come there is no combustion?
« Reply #4 on: September 24, 2019, 05:26:42 AM »
Combustion is in the presence of oxygen gas .In combustion also energy is eleased .But explosion is not always combustion.If explosion is after reaction with oxygen then it is combustion.However if it is not in the presence of oxygen then it is not combustion.

Offline Borek

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Re: How come there is no combustion?
« Reply #5 on: September 24, 2019, 06:50:12 AM »
Combustion is in the presence of oxygen gas .In combustion also energy is eleased .But explosion is not always combustion.If explosion is after reaction with oxygen then it is combustion.However if it is not in the presence of oxygen then it is not combustion.

Thank you Captain Obvious for not letting the OP to find the answer on their own.
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Offline INeedSerotonin

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Re: How come there is no combustion?
« Reply #6 on: September 24, 2019, 07:51:02 AM »
I initially thought that the fuel would be the TNT itself, but you're right, I couldn't think of anything to be the oxidant. If it were oxygen, then TNT would eventually explode because of its contact with air, and it wouldn't be as useful. But yeah, I couldn't see any O2 in the reaction, so it's not it.

So none of the non-combustion explosive reactions could be a redox reaction, right?

I did some research and read that TNT explodes when it achieves the necessary activation energy, and that it is usually derivated from another explosion from another compound, which usually happens because of a struck or if an electric discharge is passed through it

Very fascinating!

Thank you guys for your help ;)
« Last Edit: September 24, 2019, 08:01:46 AM by INeedSerotonin »

Offline AWK

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Re: How come there is no combustion?
« Reply #7 on: September 24, 2019, 11:25:08 AM »
Quote
So none of the non-combustion explosive reactions could be a redox reaction, right?
There is a subset of redox reactions called disproportionation reactions
AWK

Offline Enthalpy

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Re: How come there is no combustion?
« Reply #8 on: September 30, 2019, 05:24:12 PM »
Combustion is in the presence of oxygen gas.

I've seen the word "combustion" used with chlorine. "Oxidation" doesn't need oxygen, as the term drifted to a more general meaning.

Offline Enthalpy

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Re: How come there is no combustion?
« Reply #9 on: September 30, 2019, 05:37:47 PM »
[...] If there is an explosion, isn't there a combustion? [...]

An explosion doesn't even need an oxido-reduction. Some allotropes can explode just by rearranging the crystal
https://en.wikipedia.org/wiki/Explosive_antimony
and researchers try to synthesize octaazacubane, the N8 cubical analogue to cubane, that would rearrange explosively to 4N2.

Offline INeedSerotonin

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Re: How come there is no combustion?
« Reply #10 on: September 30, 2019, 05:43:13 PM »
[...] If there is an explosion, isn't there a combustion? [...]

An explosion doesn't even need an oxido-reduction. Some allotropes can explode just by rearranging the crystal
https://en.wikipedia.org/wiki/Explosive_antimony
and researchers try to synthesize octaazacubane, the N8 cubical analogue to cubane, that would rearrange explosively to 4N2.

This is fascinating! Thank you!

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