Saturated solution at equilibrium (1 Viewer)

[qna]

How can a solution right at the point of saturation be at equilibrium if there is no visible solute, since there are equal rates of dissolution and recrystallisation shouldn't the amount of solid solute be equal to the aqueous solute?

 

[qna]

Also, why is it that the concentration of products and reactants at equilibrium is not equal, even in reactions with 1:1 mole ratios?

 

[qna]

bump

 

[mato915]

idk my guess would be that concentration doesnt equal rate? like equal rate of precipitate forming and dissociation but not equal concentrations; like position of equilibrium doesnt lie in the middle?

 

[wizzkids]

For a solution to be saturated, and at equilibrium, by definition there must be some excess solid solute.
It is not the amounts or the concentrations of solid and dissolved solute that are the same.
In fact, we can't really talk about a concentration value for a crystalline solid.
All you need is half a gram of solid in the bottom to maintain saturation in half a litre of solution; that is enough (provided the system is well mixed).

 

[wizzkids]

To understand why the position of equilibrium does not correspond to equal molar concentrations of products and reactants, this could only occur if the rates of the forward and reverse reactions are exactly matched at the equimolar concentrations. This almost never occurs. One reaction is usually faster than the other (measured in moles per second).
Watch this YouTube clip see if that helps.
Modeling Dynamic Chemical Equilibrium