0
$\begingroup$

If a system is in chemical equilibrium is it possible to put the system out of its current state by introducing novel substances not present in it whose behavior isn't analogous to the one of the substances already in the system and whose interactions can start new reactions unseen by the system till the moment the new substance is added? Can even a miniscule concentration of that substance (so miniscule it could be as small as even 1 molecule) start dramatic changes capable of affecting the entire system?

To be clearer I would like to show an example. Imagine there is a system of substances all of the reactions among which have already reached equilibrium rates and the concentrations of their reagents and products are stable. Then, we add extra reagent not present in the system until that moment capable of interaction with its components to form novel molecule which on its turn is able to further interact with the components of the system to form other novel molecule and it can further interact with components of the system and so on until a molecule so large is formed that it splinters into 2 molecules. However, each of these molecules is further able to interact with components of the system to produce a "new generation" of large molecules which when a certain limit is reached splinter into 2 whose properties, however, are identical to the 2 molecules already described, so in the end novel substances emerge able to dramatically shift the equilibrium in which the system was before their addition. Then, is this example possible proof of the ability of even a single molecule to start a chain of reactions able to shift chemical equilibriums and is it a proof there can be systems appearing to be in the state of equilibrium but actually able to undergo great changes if the appropriate molecules are added to them?

Basically, the purpose of my question is to ask (if it's even possible) to have a system which has reached a state of chemical equilibrium stable in time but which can be radically altered by a reagent not characteristic for it by even a minute concentrations of that reagent. A perfect example of my point is a sterile growth medium. By all means it's in state of chemical equilibrium. All possible reactions able to occur in it are already occurring with equal speeds of the forward and reverse reactions with concentrations of their reagents and products already in equilibrium. As such there is nothing new that can occur in the system if we rely only on the natural processes able to develop in it. However, if we add even 1 bacterium able to grow in the medium many new reactions will start to occur as a result of its metabolism and it can dramatically change the entire system bringing it out of the state it was able to occupy for extremely long periods of time without it. To my mind the growth medium is in a state of chemical equilibrium and there is no way to suddenly develop a bacterium on its own, therefore, our perception of chemical equilibrium entails us with a certain degree of predictability we prescribe to systems actually able to undergo drastic changes if the "right kind" of reagents are added to them even in extremely minute concentrations, even for extremely large systems. Is my interpretation of chemical equilibrium correct? Am I misunderstanding something here?

Furthermore, if it's correct does it means there are possible systems whose path of evolution can be entirely unpredictable but they could appear stable in time? What if the difference between their long-term stability and the myriads of unpredictable states they can occupy is a single molecule of complexity unable to be produced by the system itself? Does it mean, then, that chemical equilibrium alone isn't a measure of the possible states of the system but only an approximation to what is currently possible under certain physical conditions for a mixture of reagents? Then, does it means there is a "limit of opportunity" for any system in equilibrium defining what is possible for the system currently, but not all that is possible for it under the physical conditions it's in? Finally, does it means certain substances can change this "limit of opportunity" by generating novel compounds and starting novel reactions taking the system out of its current state without the need for addition of new reagents for the system? Is that possible for any known chemical (I'm referring to chemistry alone here and not mentioning any equilibrium changes induced by biological agents) systems and what are these examples?

I'm looking for both a system and a reagent capable of displaying such behavior to explain a quest of mine. I'm thinking about the possibility of the existence of "cascade reactions" able to dramatically change systems already in stable, e.g. equilibrium, state but the compound causing the initial reaction in the cascade shouldn't be native to the system and it shouldn't be able to produce it on its own. I'm thinking about the existence of limits to the reactions possible under certain conditions induced not by the conditions themselves but by the levels of complexity the products of the reactions currently occurring in the system can reach. I mean if the reagents are relatively simple substances combining to produce relatively simple products then the system can reach a level of complexity where all reactions are in equilibrium under the given conditions but not all possible reactions that these reagents could participate in have occurred. Then, if we add even a single molecule of novel substance with a higher degree of complexity than the ones in the system, could it trigger this "cascade" of reactions leading it to a higher degree of complexity than it used to have? What if in this new state of more complex chemistry we add 1 more molecule with even a higher degree of complexity? If we repeat the process over and over again how far can we get? Could we react a state where the entire system itself can begin selfreplicating its complexity and even evolving further complexity on its own without further outside intervention? If this is possible then the purpose of my question is to understand in what systems at what state what kind of molecule can trigger such transition? If it isn't possible I want to know why and at what level of complexity such a transition stops? Basically, I my motivation is to understand where is the border when biology and chemistry meet and is concept of a break in chemical equilibrium triggered by even a miniscule amount of the "right" kind of complexity crucial to finding it?

P.S. I hope now my question is clear enough to attract good answers and be unblocked.

$\endgroup$
  • $\begingroup$ Discussion moved to chat. Please try to keep back and forth to a minimum, even when it's a productive exchange like this one was. $\endgroup$ – jonsca Oct 3 '17 at 23:17
2
$\begingroup$

Nobody cares about a single molecule, so let's say "a very small quantity" instead. Well, then the answer will be along the following lines:

  1. Small influences produce small changes. In particular, that small addition will bring your system to a new equilibrium (another state, if you'd like), but it would be infinitesimally close to your initial one.
  2. Alternatively, if one tiny droplet will make the system run out of control and finally end up somewhere pretty far from the initial state, this means it was never in equilibrium in the first place.
  3. In this last case, in particular, the added droplet might not have been necessary. Sooner or later, a huge enough fluctuation would do the same.

As an example of a system in the "seemingly, but not really stable" state, think of those effervescent tablets. They just sit on the shelf and do nothing, but add a very tiny amount of water and see what happens.


To sum it up, out notion of stability is pretty solid. There very much is the state of stability for any system; it is the only one, and it can't be dramatically changed by addition of one molecule of anything. In some systems this state may be hard to reach, but that's another story.

So it goes.

$\endgroup$
  • 1
    $\begingroup$ What about a system where all reactions are in equilibriums between the forward and reverse reaction and then if we add just one molecule of some substance this can start a chain reaction of generation of novel substances which spin the system into a totally different state. Then was the initial system not in equilibrium? But then it had all of its reactions at equilibrium concentrations of reagents and products. If that was the case, then, do I missunderstand something about the concept of chemical equilibrium at the first place? $\endgroup$ – Yordan Yordanov Sep 27 '17 at 20:30
  • $\begingroup$ The other way to look at this is significant figures. The mass of a proton is known to about 13 parts per billion. I doubt that any equilibrium constant is known to that precision. $\endgroup$ – MaxW Sep 27 '17 at 20:34
  • 1
    $\begingroup$ @Yordan If your system had all reactions, then it would have the said chain reaction too, and the chain reaction would develop and carry the system away from that state. If it didn't have the chain reaction (despite its being theoretically possible), then the system was not in equilibrium. $\endgroup$ – Ivan Neretin Sep 27 '17 at 21:01
  • 1
    $\begingroup$ @IvanNeretin, but how can it had this reaction if it didn't had the compound which started it? Do you infer all compounds that can be synthesized under certain conditions are synthesized under the said conditions irrespective of the complexity of interactions required to synthesize them? What if the synthesis of the compound that could change completely the system has such a low probability that it would take a system many times larger than the visible universe to wait for trillions of trillions of years to produce even a 1% of chance to create the change inducing molecule? $\endgroup$ – Yordan Yordanov Sep 27 '17 at 21:12
  • 1
    $\begingroup$ For all we can see the system is in equilibrium for all that time, but do you say that our perception is deceiving and system is actually not in equilibrium although all we can measure about it says it is? Are you saying then, that systems which look stable throughout time from our current perception of chemistry aren''t but are just like clockwork devises waiting for their chance to burst into a totally unpredictable states which we couldn't even imagine and we actually never see they turn into our real world? Is that the correct interpretation of the concept of chemical equilibrium,then? $\endgroup$ – Yordan Yordanov Sep 27 '17 at 21:17

Not the answer you're looking for? Browse other questions tagged or ask your own question.