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Author: Subject: What is phosgene/phosphine?
Yttrium2
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[*] posted on 30-7-2019 at 18:07
What is phosgene/phosphine?


Doesn't one of them ignite when it comes into contact with air?

If so how was it used as a war gas? Just out of curiosity?
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[*] posted on 30-7-2019 at 18:11


Quote: Originally posted by Yttrium2  
Doesn't one of them ignite when it comes into contact with air?

If so how was it used as a war gas? Just out of curiosity?


https://en.wikipedia.org/wiki/Phosgene
https://en.wikipedia.org/wiki/Phosphine




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draculic acid69
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[*] posted on 31-7-2019 at 02:53


Two different things,both very nasty gasses
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[*] posted on 31-7-2019 at 02:56


I can't believe someone with >400 posts would ask such wikiable questions...

[Edited on 190731 by fusso]




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[*] posted on 31-7-2019 at 04:52


Quote: Originally posted by fusso  
I can't believe someone with >400 posts would ask such wikiable questions...

[Edited on 190731 by fusso]

Ahh then. You haven't met Yttrium2 yet. Our prolific questioner.
Everyone has their own quirks. Even you.

I quite like Y2's questions - or at least some of them because they often remind me of stuff I have not thought of for a while.




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Yttrium2
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[*] posted on 31-7-2019 at 06:54


Thanks, JSum


I guess I could have wikipediaed it, I tried youtubing it and I don't see any images or videos that looked legit.

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[*] posted on 31-7-2019 at 07:33


... the Wikipedia article was suitable. I got to see the molecule, but not it's color!!!

...

Next question,

What properties distinguish the volatility of a chemical? For instance what makes amnonia so volatile and pervasive as compared to H2O?
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[*] posted on 31-7-2019 at 07:54


https://opentextbc.ca/introductorychemistry/chapter/intermol...



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[*] posted on 31-7-2019 at 09:40


Quote: Originally posted by fusso  
I can't believe someone with >400 posts would ask such wikiable questions...

[Edited on 190731 by fusso]


I almost choked on the irony.

@Yttrium2: Volatility describes the propension of a substance to evaporate. So the key property is the vapor pressure of the substance, which is related to the boiling point. You're talking about the pervasiveness of ammonia, so maybe the odor detection threshold could be considered when talking about the perceived volatility, although strictly it has nothing to do with it.
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[*] posted on 31-7-2019 at 09:49


That's what I figured ^


Was wondering though what makes the BP the way it is, and I'll have to review my notes *cough* on intramolecular forces (damn, I had everything saved but my computer got dismantled by some tweaker)



I could read the article that was posted, but I should probably stop right here--and focus.
Focus on the math that needs to be done that is holding me back. Pretty soon I will be getting a new computer so I can get back to work on the khanacademy.


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It's IUPAC!


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[*] posted on 31-7-2019 at 09:57


Quote: Originally posted by Yttrium2  
... the Wikipedia article was suitable. I got to see the molecule, but not it's color!!!

They're colorless. For colors, you want phosphenes:
https://en.wikipedia.org/wiki/Phosphene




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[*] posted on 31-7-2019 at 19:21


Quote: Originally posted by Yttrium2  
That's what I figured ^


Was wondering though what makes the BP the way it is, and I'll have to review my notes *cough* on intramolecular forces (damn, I had everything saved but my computer got dismantled by some tweaker)



What you want is intermolecular forces.

For a start, comparing ammonia with water is not comparing like with like. The way we usually handle ammonia is in a water solution. Comparing liquid ammonia at negative 35C with liquid water at RT is difficult since the kinetics differs so much at those tempertatures.

In any case, the particular intermolecular force that is dominant here is hydrogen bonding. And this is significantly stronger between water molecules than between ammonia molecules.

A really interesting exercise is to look up the MP for hydrides of the P-block elements and plot them on a graph. You really see the effect of hydrogen bonding.
That is,
  • For HF, HCl, HBr, HI, plot melting point against period.
  • Do the same for H2O, H2S, H2Se, H2Te
  • And again for NH3, PH3, AsH3, SbH3
  • Finally do the same with CH4, SiH4, GeH4, SnH4

    In each case you get an approximately straight line, but the first item in the graph bucks the trend with a much higher MP. This is evidence of the hydrogen bonding.
    You can also see that H bonding is greatest with fluorine, less with oxygen, even lower with nitrogen and negligible with carbon.

    (This leads directly to the conclusion that oxygen-contaning compounds are the ones where hydrogen bonding is most likely to be a significant consideration. Basically because there is only one fluorine compound can exhibit hydrogen bonding: HF. Single bond and all that. R-OH opens up numerous more possibilities.)




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    [*] posted on 31-7-2019 at 20:29


    Quote: Originally posted by j_sum1  

    A really interesting exercise is to look up the MP for hydrides of the P-block elements and plot them on a graph. You really see the effect of hydrogen bonding.
    That is,
  • For HF, HCl, HBr, HI, plot melting point against period.
  • Do the same for H2O, H2S, H2Se, H2Te
  • And again for NH3, PH3, AsH3, SbH3
  • Finally do the same with CH4, SiH4, GeH4, SnH4

    In each case you get an approximately straight line, but the first item in the graph bucks the trend with a much higher MP. This is evidence of the hydrogen bonding.
    You can also see that H bonding is greatest with fluorine, less with oxygen, even lower with nitrogen and negligible with carbon.


  • You want boiling points, not mp, and you'll find that water has a greater effect than HF, simply because it have have two hydrogen bonds to neighbours (while HF is limited to one).




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    [*] posted on 31-7-2019 at 20:54


    You may be right on the BP/MP thing. I have done it with both and I recall the difference being more obvious with MP. But I may have remembered wrongly.
    Ditto on the HF/H2O thing. I may have misremembered details. I do have my graphs around somewhere.

    I do remember when I produced and studied these graphs and also thought about the number of H bonds possible... I remember feeling like i had understyoof hydrogen bonding properly for the first time. It was a nice moment.




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    [*] posted on 1-8-2019 at 19:42


    H-bonding is a model that explains one aspect of the behaviour of the elements, it hasn't as yet been ditched for a model that explains some aspects better.
    There are some who strongly disagree with any notion of H-bonding being a real thing, Huckabeee-Sanders, Trump etc, not many others....its an excellent model to explain something that makes no sense, i say this because the nature of this 'force' has never even been attempted to be explained/substantiated, we just go ok itll do. Maybe one day when TOE clearly crystallizes in the augmented mind of a future genius we will know more but for now there is no more!!
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    [*] posted on 1-8-2019 at 21:06


    H bonding is a useful descriptor of an observable phenomenon.

    From a practical stand point it does not need to be nailed dpwn to one mechanism. It just needs to be consistent.




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    [*] posted on 2-8-2019 at 10:27


    Quote: Originally posted by Heptylene  
    ......

    You're talking about the pervasiveness of ammonia, so maybe the odor detection threshold could be considered.......



    The topic of odor detection is, in my opinion, complex, to quote a source (https://www.webmd.com/brain/qa/how-does-my-sense-of-smell-wo... ):

    "A person's sense of smell is driven by certain processes. First, a molecule released from a substance (such as fragrance from a flower) must stimulate special nerve cells (called olfactory cells) found high up in the nose. These nerve cells then send information to the brain, where the specific smell is identified."

    So, we have limiting factors as to what one can smell based on the existence of the appropriate olfactory cells, and then by the ability of our human computer brains to translate the sensation.

    Some of the latter brain programming may be hardwired from hundred of thousands of years in our evolution. Also, there could be random DNA changes to our genes relating to number of olfactory cells and subsequent impact on relative survival rates.

    Now, in the case of ammonia, which is produced as byproducts of living animals, I would guess for survival reasons, like relating to the detection of the presence of predators, diseases from dead animals,..., it is an important smell to detect. It may be possible that we can detect even low concentrations of ammonia, becomes it is part of our evolutionary survival skill set.

    Cool stuff (wait, that's the sense of touch...).
    ----------------------------------------------------

    Did find a study on the detection limits for ammonia based on odor detection thresholds (ODTs) and lateralization threshold (LT, where the lateralization refers to irritation sensitivity in either the right or left nostril), source https://academic.oup.com/chemse/article/32/1/11/361356 to quote:

    "With the mean ODT being 2.59 ppm (mean log value = 0.41, SD = 0.97, not in Table 2), the mean LT of 43.94 ppm (mean log value = 1.64, SD = 0.60, not in Table 2) was significantly higher. The effect of Week was significant (Z = 2.06, P = 0.04), with the mean threshold being lower during the second assessment (MW2 = 8.76, mean log value = 0.94, SD = 1.12, not in Table 2) than during the first (MW1 = 12.96, mean log value = 1.11, SD = 0.89, not in Table 2). However, this effect was no longer significant after exclusion of one subject who had an extremely low ODT of 0.019 ppb during the second static olfactometry assessment (Z = 1.74, P = 0.08)."

    Interestingly, one individual was able to seemingly detect 10 parts in a trillion of ammonia, wow, that may be a discovered example of an evolutionary leap of mankind to eschew an environment increasingly suffering from chemical pollution!

    [Edited on 3-8-2019 by AJKOER]
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