[miaou5]

Given the definition of a "saturated solution" (i.e., that no more solute can be dissolved in the solution before it will begin precipitating), why does a reaction at equilibrium mean that the solution is saturated? Since ostensibly at equilibrium some of the dissolved ions will be recombining to form the solid (aka the reverse reaction), doesn't that mean that a some of the solvent in the solution IS ALREADY IN PRECIPITATE (aka solid) FORM? (And doesn't that fly in the face of the definition of saturated solution, which--as stated above--refers to the soln BEFORE the solvent begins to precipitate?) I've been sorely confused by this matter, and any help would be much appreciated. 

[Borek]

You are writing strange things, hard to understand what you mean.

Given the definition of a "saturated solution" (i.e., that no more solute can be dissolved in the solution before it will begin precipitating), why does a reaction at equilibrium mean that the solution is saturated?

What reaction?

Since ostensibly at equilibrium some of the dissolved ions will be recombining to form the solid (aka the reverse reaction), doesn't that mean that a some of the solvent in the solution IS ALREADY IN PRECIPITATE (aka solid) FORM? (And doesn't that fly in the face of the definition of saturated solution, which--as stated above--refers to the soln BEFORE the solvent begins to precipitate?)

Solvent doesn't precipitate, solute does.

[fledarmus]

Are you talking, for example, about a reaction like

NaCl(s) <===> Na⁺(aq) + Cl^-(aq)  ?

For the Na⁺ and Cl^- ions to combine in an aqueous solution, they have to shed the layers of water which surround them, the dipoles of the water molecules being attracted by the charges of the ions. Once they combine, they are no longer in solution and form a solid precipitate.

If the solution is not saturated, there will be no solid NaCl in the mixture. Any sodium chloride added to the water will dissolve to form the aqueous ions, but no NaCl will be precipitating. The reaction is not yet at equilibrium. Once enough NaCl is added to totally saturate the solution with ions, you set up a dynamic equilibrium between the ions and the solid - as fast as solid NaCl dissolves to form the aqueous ions, aqueous ions will combine to form solid.

[miaou5]

Are you talking, for example, about a reaction like

NaCl(s) <===> Na⁺(aq) + Cl^-(aq)  ?

For the Na⁺ and Cl^- ions to combine in an aqueous solution, they have to shed the layers of water which surround them, the dipoles of the water molecules being attracted by the charges of the ions. Once they combine, they are no longer in solution and form a solid precipitate.

If the solution is not saturated, there will be no solid NaCl in the mixture. Any sodium chloride added to the water will dissolve to form the aqueous ions, but no NaCl will be precipitating. The reaction is not yet at equilibrium. Once enough NaCl is added to totally saturate the solution with ions, you set up a dynamic equilibrium between the ions and the solid - as fast as solid NaCl dissolves to form the aqueous ions, aqueous ions will combine to form solid.

thanks so much! that makes sense. exactly what i needed. thanks again.