7.6 Solubility Equilibria Flashcards
What is solubility
- Quantity of solute that dissolves in a quantity of a solvent at a particular temperature
- Concentration of a saturated solution at a particular temperature
Example of solubility
How much sugar can dissolve in water at 100 degrees celcius
What is the purpose of consuming barium sulfate + water before an x-ray
- Its low solubility allows it to remain a solid in one’s body, and the solid (undissolved) crystals create a clear image of the digestive tract
- Barium ions are toxic if dissolved, so knowing its poor solubility helps us know its safe to consume
What do ionic compounds form when placed into water
A dynamic equilibrium
What happens to an ionic compound like AgI in water
Since it has low solubility, its ions remain tightly packed in a crystal lattice
How does water try to dissolve an ionic compound (ex. AgI)
The charged ends of polar water molecules orient themselves around opposite charged ions to pull them into solution (ex. Partial negative oxygen orients around positive silver ions)
What are the forward and reverse reactions of
AgI (s) → Ag+ (aq) + I- (aq)
Forward: Dissolution
Reverse: Precipitation
When a solution is saturated, it has reached…
Equilibrium
Define saturation
When a solvent contains the max amount of solute at a certain temperature and pressure, and concentrations remain constant
Define solubility equilibrium
A dynamic equilibrium between a solute and a solvent in a saturated solution in a closed system
Is a solubility equilibrium heterogenous or homogenous
Heterogenous: Between a solid ionic compound and its aqueous ions
Why can AgI (s) be ignore in the equilibrium law equation
It’s a solid, has constant concentrations
What is Ksp
The solubility product constant from the equilibrium law equation of a saturated solution at a certain temperature
When does the solubility of an ionic compound vary
Depending on the ions it contains
How do highly charged anions and cations do and why
They make a compound less soluble because it takes more energy for the solvent to break its crystal lattice
Compare solubility of divalent to monovalent ions
Divalent ions such as calcium and carbonate are less soluble than monovalent ions such as nitrate and sodium
What happens when 2 aqueous solutions mix
They can form an ionic compound with low solubility that precipitates out of the solution
What happens if you pair a cation with an anion vs another cation
Cations + anions: Might be soluble
Cations + Cations: Insoluble
A precipitate forming depends on…
Concentrations of the ions
What is the trial ion product
Product of concentrations of ions raised to powers of coefficients to determine if precipitation occurs
If Q > Ksp…
Rxn shifts left and precipitation occurs
If Q < Ksp…
Rxn shifts right and no precipitation occurs
If Q = Ksp…
Solution is at equilibrium, no precipitation occurs
What is the common ion effect
By adding a common ion that it’s in ionic compound to a dissolution system, you can make the reaction shift left and form a precipitate
A precipitate will only form after the common ion effect if..
The new concentrations of aqueous ions push the equilibrium past the solubility limit represented by Ksp
What kind of solutions can the common effect occur in
Any in between solutions of low and high solubility
Would silver acetate be more or less soluble in silver nitrate or water
Since silver nitrate has a common ion, it will make silver acetate less soluble than in water due to the common ion effect
Define phase equilibrium
Equilibrium between different physical states
Ex. Bromine equilibrium
What happens when a dissolving substance reaches equilibrium
It stops dissolving
Do highly soluble compounds form an equilibrium
No
