Solubility

|| SOLUBILITY
Solubility
Refers to the maximum amount of solute that can be dissolved in a given quantity of solvent at a certain temperature.
Sol: >10g/L
Sparingly Sol: between 1g/L and 10g/L
Insol: <1g/L
What dissolves what?
Polar dissolves polar
Non – polar dissolves non polar
When a salt is placed in water, the positive and negative ions become surrounded by water molecules – become hydrated.
What dissolves in water?
Insoluble – do not dissolve
Ionic – dissociate: water pull ions from solid structure to form a solution. Conduct electricty
Polar - ionisation: (may) react with water to form ions – acids and bases
Polar – dissociation: form hydrogen bonds.  do not conduct electricity
Saturated solution
A solution that no more solute can be dissolved in at that temperature.
Unsaturated solution
A solution that contains less solute than is needed to make it saturated at a given temp.
Crystalisation
Process by which solute comes out of solution.
Occurs when the temperature of the solution decreases.
Supersaturated
An unstable solution that contains more solute than should have dissolved at the given temperature.
Occurs when a saturated solution is cooled very slowly and carefully so crystalisation does not occur.
Concentration
Dilute: high solvent to solute ration
Concentrated: low solvent to solute ratio
Solubility curves
Shows relationship between solubility and temperature.
Boling point elevation and freezing point depression
Boiling: the solute ‘refuses’ o enter gas phase, preventing the solvents ability to also enter gas phase.
Freezing: the solute prevents the solvent from forming its frozen lattice structure.
Solubility of gasses
Polar gasses dissolve easily in water
Solubility of a gas in a liquid depends on temperature of solvent and the pressure of the gas above the solvent.
Increasing temp = deceasing solubility
Increasing pressure = increasing solubility
Molarity
Measure of concentration in terms of moles.
The number of moles of solute per liter of solution
Precipitation reactions
A solid is produced during a reaction between two clear solutions of ionic molecules.
Complete: show all ions present
Net Ionic: show only the ‘active’ ions
Solubility Rules
All salts of Na+ K+ and NH4+ are soluble, as are all nitrates (NO3-)
All –ides of Cl- Br- and I- are soluble except with silver and lead
All sulfates SO42- are soluble unless wih silver lead calcium strontium or barium
All phosphates and carbonates are insoluble unless with G1 elements or ammonium
All hydroxides are insoluble except with G1&2 elements and ammonium and barium
All sulfides are insoluble except with G1&2 elements and ammonium
More rules
The rules imply that a compound is soluble or insoluble. In reality they are all soluble, but to a varying degree - some very some hardly at all.
Precipitation Reaction

AB(aq)+CD(aq) èAD(s)+CB(aq)

Net ionic:
A+(aq)  + D-(aq) à AD(s)

Precipitation occurs when a cation and anion from different solutions form an insoluble compound.
1.           Rearrange pairs to form products
2.           Using solubility table, determine preciptiate. If no preciptate forms, there is no reaction
3.           Write the state that the two products are in (aq for the “liquid” one, and s for the precipitate)
4.           Determine charges of each element
5.           Balance charges of each product pair, then balance equation



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