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How could we be sure that one certain reaction in equilibrium is dynamic? Since there would be no visible change in vessel, which property of the reaction would provide a proof besides color? Which laboratory technique could be used?

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  • $\begingroup$ Since during static equilibrium neither macroscopic nor microscopic particle are change and in dynamic equilibrium the macroscopic particles don't change but the microscopic do so a device which can measure properties at a microscopic level can detect if something is in dynamic or static equilibrium. For a chemical reaction you can observe with a microscope wether is there is any movement between the reactants and the products. Or a spectroscope may be used since the amount of energy released during may emit light at lower or higher wavelengths that our eyes can perceive. $\endgroup$ – Agyey Arya Apr 14 '15 at 18:38
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    $\begingroup$ I don't get it - equilibrium of reaction is always dynamic - static would mean there's no reaction. $\endgroup$ – Mithoron Apr 14 '15 at 18:48
  • $\begingroup$ Mmmmmmm, this seems too much like a comment to me. The main Q you should be answering is what's the difference between dynamic and static equilibrium?, while instead of elaborating on that part you only add a mere sentence and then add some irrelevant info. $\endgroup$ – It's Over Apr 14 '15 at 19:09
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My answer starts with the premise that a static equilibrium exists (although that is debatable).

How could we be sure that one certain reaction in equilibrium is dynamic?

If your reaction is at dynamic equilibrium, changing the temperature or the concentration of one of the reactant or product species (by adding some solute, for example) should disturb the equilibrium. You would see a net reaction, i.e. change in the concentrations of species in solution or in the gas phase. The reason you did not see any changes before is that the forward and reverse reaction were occurring simultaneously at the same rate.

Since there would be no visible change in vessel, which property of the reaction would provide a proof besides color? Which laboratory technique could be used?

Color would not help either, unless you disturb the equilibrium first. Once you disturb it, any method sensitive to changes in concentration will give you evidence, as will calorimetric methods.

[Devils advocate question]: What about static reaction equilibrium?

If your reaction is at static equilibrium, changing the temperature or the concentration of one of the reactant or product species, in contrast, would not result in any macroscopic change. For example, if you lower the temperature such that the forward and reverse rate are practically zero, and then add some reactant or product, nothing would happen. Not sure why you would call it a reaction equilibrium though when the reaction never occurs under these conditions. In other words, I know of no reactions where forward and reverse reactions suddenly stop with reactants and products still present under conditions where the reaction proceeded to reach equilibrium.

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