C11-4-10 SOLUBILITY AND PRECIPITATION OUTCOME QUESTION(S): C11-4-10 SOLUBILITY AND PRECIPITATION Explain which factors can affect solubility of solids, liquids, and gases Differentiate among saturated, unsaturated, and supersaturated solutions using a graph of solubility data and solve problems Explain solubility and precipitation using balanced ionic and net ionic equations Use a table of solubility rules to predict the formation of a precipitate Vocabulary & Concepts 

Factors that affect Solubility Nature of the Solvent and Solute The general dissolving rule is like dissolves like Remember that solubility is a relative term Solute Solvent Polar Non-polar Ionic √ X

2. Surface area (crushing) Dissolves faster with increased surface area Amount dissolved depends on level of attraction Agitate (stir) the mixture Added energy of stirring increases dissolving Dissolving requires energy (endothermic process)

Increasing temperature of solids in a solvent increases solubility. 4a. Temperature Increasing temperature of solids in a solvent increases solubility. Adding heat provides needed energy to separate the solute and solvent particles H O - + H O - + H O - + H O - + H O - + H O - + H O C + - H O C + - H O C + - H O C + - H O C + - Attractive Force

4b. Temperature Increasing temperature of gases in a solvent decreases solubility. FLAT The increased temperature gives the dissolved gas particles the energy needed to overcome attractive forces and escape

5. Pressure (only affects gases) Increased pressure on gas solute increases solubility in a solvent. Forces gas particles into contact with the liquid Gas particles are high energy and only have a weak attraction to solvent particles – this is easily overcome…

Data showing the relationship between solubility and temperature. Solubility Curve Data showing the relationship between solubility and temperature. Solubility curves show saturation amounts for a solute dissolving in 100 g of H2O over a range of temperatures Water has a density of 1 g/ml: 100 g of H2O is 100 mL Solubility generally increases with temperature – but exceptions exist

At 50oC: 100 g H2O is saturated with 90 g of KNO3 dissolved Solubility creates three types of solutions: 1. Saturated Maximum amount dissolved at that temperature At 50oC: 100 g H2O is saturated with 90 g of KNO3 dissolved 2. Unsaturated Could still dissolve more at that temperature 3. Supersaturated Special case - Holding more than expected at that temperature

Supersaturation is achieved using temperature and patience… 100 g of glucose was placed in a beaker of water: Heat Bump, shake, add seed crystal Stir Supersaturated solutions are very unstable

Use proportions to find missing values How much can be dissolved in 500 mL? Solubility is directly proportional to volume 30 g 250 mL 500 mL Saturated Saturated 30 g = g 250 mL 60 (500 mL) (500 mL) 500 mL Use proportions to find missing values

2.5x the solvent can dissolve 2.5x the solute. If 25.0 g of solute saturates 40.0 g of solvent, what is the solubility in 100 g of solvent (at the same temperature)? Use proportions Make a prediction… grams of solute1 = grams of solute2 grams of solvent1 grams of solvent2 25.0 g1 = g2 40 g1 62.5 (100 g2) (100 g2) 100 g2 2.5x the solvent can dissolve 2.5x the solute.

grams of solute1 = grams of solute2 If 30.1 g of solute dissolves in 350.0 mL of water, what is the solubility in 100g of water (at the same temperature)? Make sure units match… Water has a density of 1 g/ml: 100 g of H2O is 100 mL grams of solute1 = grams of solute2 grams of solvent1 grams of solvent2 30.1 g1 = g2 350.0 mL1 8.60 (100 g2) (100 g2) 100 mL2 About ¼ the solvent can dissolve about ¼ solute.

About 2x the solute requires about 2x the solvent. What volume of water is required to dissolve 240 g of KNO3 at 60°C? grams of solute1 = grams of solute2 mL of solvent1 mL of solvent2 113 g1 240 g2 Make a prediction… 212 g2 = 100 g1 ? g2 About 2x the solute requires about 2x the solvent. Create a proportion using the information from the graph for the given temperature = 240 g2 ? g2 100 g1 113 g1 113

75 mL of a saturated solution of KNO3 at 70°C is cooled to 40°C 75 mL of a saturated solution of KNO3 at 70°C is cooled to 40°C. What amount will precipitate out? Use proportions Lowering temperature lowers solubility = 75.0 mL2 100 mL1 140 g1 105 g2 ? g2 At 70oC: Ask: What does “saturated” look like for this volume of solvent? = 75.0 mL2 100 mL1 65 g1 49.5 g2 ? g2 At 40oC: 105 g – 49.5 g = 55.5 g will precipitate out 140 65 70

C11-4-10 SOLUBILITY AND PRECIPITATION CAN YOU / HAVE YOU? C11-4-10 SOLUBILITY AND PRECIPITATION Explain which factors can affect solubility of solids, liquids, and gases Differentiate among saturated, unsaturated, and supersaturated solutions using a graph of solubility data and solve problems Explain solubility and precipitation using balanced ionic and net ionic equations Use a table of solubility rules to predict the formation of a precipitate Vocabulary & Concepts