Kinetic equilibrium of chemical reaction

AI Thread Summary
The discussion centers on the dynamics of a reversible chemical dissociation reaction, specifically AB ↔ A⁺ + B⁻, where the dissociated form is soluble while the undissociated form precipitates. It highlights that the reaction proceeds more rapidly to the left due to the greater reaction surface area of the dissolved form compared to the precipitate, which can only react at its surface. The conversation also touches on the concept of reaction equilibrium, noting that it can be misleading as it does not necessarily indicate the stability of reactants or products. The relevance of this idea is questioned, particularly regarding whether a solid clot can dissociate in a solvent if it cannot dissolve. The discussion acknowledges that while solids react only on their surfaces, this does not imply that precipitation reactions are inherently faster. Additionally, the equilibrium for such reactions, known as the solubility product (Ksp), varies significantly among different compounds, with some having very low Ksp values, indicating limited solubility.
sludger13
Messages
83
Reaction score
0
I was thinking about this:

Let's consider a dissociation of some chemical that can run in both directions:
AB\rightleftharpoons A^{+}+B^{-}
Dissociated form is soluble in a solvent and undissociated form is not - it precipitates.
Then the reaction proceeds to the left much faster than to the right, because dissociated form possesses much more reaction "surface" (it is dissolved) than a clot (clot reacts only on its surface).
Also a reaction equilibrium moves almost entirely to the left, because reaction conditions (matter phase) differ from one reaction's side to another. Also the reaction equilibrium does not reflect the stability of reactants resp. products, so it's kinda false (or kinetic) equilibrium.

Is this relevant idea in fact? Can some clot placed inside solvent dissociate but dissociated form does almost not exist in the solvent because of this?
Or is this true - if any chemical cannot be dissolved by a solvent, it can be neither dissociated by a solvent?
 
Chemistry news on Phys.org
sludger13 said:
Then the reaction proceeds to the left much faster than to the right, because dissociated form possesses much more reaction "surface" (it is dissolved) than a clot (clot reacts only on its surface).

While you are right that solids react only on the surface, it doesn't follow that the precipitation reaction is much faster.

Also a reaction equilibrium moves almost entirely to the left

For a weakly soluble salts - yes. But of well soluble ones - no.

Equilibrium for such a reaction is called a solubility product. Sometimes it is pretty low (predicted Ksp for PtS is something like 10-76, measured Ksp for AgI is something like 10-18), sometimes it is much, much larger (something like 25 for NH4Cl).
 
I want to test a humidity sensor with one or more saturated salt solutions. The table salt that I have on hand contains one of two anticaking agents, calcium silicate or sodium aluminosilicate. Will the presence of either of these additives (or iodine for that matter) significantly affect the equilibrium humidity? I searched and all the how-to-do-it guides did not address this question. One research paper I found reported that at 1.5% w/w calcium silicate increased the deliquescent point by...
Back
Top