Solubility

Solubility Ability of one substance to dissolve in another at a given temp and pressure Usually measured as mass (g) of solute in 100g H2O at a given temp

Saturated- max amount of solute at a given temp If more solute is added, it will not dissolve Unsaturated- less than max amount of solute at a given temp If more solute is added it will dissolve up to the point of saturation Supersaturated – more than max amount of solute at a given temp Saturated solution made at a higher temp then cooled. The solute remains dissolved in the solution. Example: Sweet Tea

Supersaturated Solutions Saturated solution made at a higher temp then cooled. The solute remains dissolved in the solution. Often if disturbed or if additional crystals (seed crystals) are added recrystallization of solute will occur The amount of solute that recrystallizes is the amount above the saturation point for the new temp Example: rock candy When cooled recrystallization occurs as the solution cools Not all solutions can become supersaturated

Solubility Curves Lines show saturation for that substance in 100g H2O at various temps Points above line supersaturated Points below line unsaturated

Go to temperature, trace up to the solubility curve of the compound you are interested in, trace across to the g/100g water. If you are reducing temperature, subtract higher temperature amount from lower temperature amount. That will tell you how much will precipitate out.

If a saturated solution of KNO3 at 80 ⁰C was cooled to 20 ⁰C, what mass of crystals would form? 170g – 30g = 140g How many g NaCl would be dissolved 100g of a saturated solution of water at 60 ⁰C? 40g What is the solubility of NaClO3 at 40⁰C? 130g If a solution at 60 ⁰C contains 110g KBr is it US, S, or SS? S

For the homework ammonia- NH3 sodium nitrate – NaNO3 potassium chloride- KCl potassium chlorate- KClO3 potassium nitrate – KNO3