Solubility and Solubility Curves

Solubility Solubility – The measure of how much solute can be dissolved in a solvent at a specific temperature. The HIGHER the solubility the MORE you can dissolve. The LOWER the solubility the LESS you can dissolve.

Definitions Solutions can be classified as saturated or unsaturated. A saturated solution contains the maximum quantity of solute that dissolves at that temperature. An unsaturated solution contains less than the maximum amount of solute that can dissolve at a particular temperature

Definitions SUPERSATURATED SOLUTIONS contain more solute than is possible to be dissolved Sometimes contain a precipitate which is a solid that crystallizes out of a solution

Effect of Temperature Think back to the demo…what happened as we increased the temperature? As we increased the temperature, we were able to dissolve more solute. GENERALLY speaking, the solubility of solids increases with increases in temperature.

Solubility Curves Solubility curves show solubility as a function of temperature for several substances on the same graph. Solubility is a characteristic property and can help you identify substances.

Solubility curve Saturated Supersaturated Unsaturated

Solubility curve Any point on a line represents a saturated solution. In a saturated solution, the solvent contains the maximum amount of solute. Example At 90oC, 40 g of NaCl(s) in 100g H2O(l) represent a saturated solution.

Solubility curve Any point below a line represents an unsaturated solution. In an unsaturated solution, the solvent contains less than the maximum amount of solute. Example At 90oC, 30 g of NaCl(s) in 100g H2O(l) represent an unsaturated solution. 10 g of NaCl(s) have to be added to make the solution saturated.

Solubility curve Any point above a line represents a supersaturated solution. In a supersaturated solution, the solvent contains more than the maximum amount of solute. A supersaturated solution is very unstable and the amount in excess can precipitate or crystallize. Example At 90oC, 50 g of NaCl(s) in 100g H2O(l) represent a supersaturated solution. Eventually, 10 g of NaCl(s) will precipitate.

Solubility curve Any solution can be made saturated, unsaturated, or supersaturated by changing the temperature.

Solubility Curves Which solid is the least soluble at 20°C? Which solid is the most soluble at 20°C? At 50°C, how much NH4Cl can be dissolved in 100 g H2O? At 50°C, how much NH4Cl can be dissolved in 300 g H2O?